A few years ago I noticed myself collapsing late in tournaments. I could win consistently early in the day (even against good opponents), maybe pick up the "random" loss to flood, screw, bad matchup, (or, you know, being out-played), run good with my back against the wall for a few hours...and then collapse in my win-and-in. I lost my win-and-in over and over despite there being nothing particularly special about my win-and-in opponents or matchups. My decision at the time was to chalk it up to old age and actual fatigue and try to switch to a less "difficult" kind of deck to play (even if I didn't like it as much). It turns out that I was experiencing a phenomenon that all of us experience; it didn't necessarily have to do with getting older. But my proposed fix actually had some sense to it.
You may have read a story in The New York Times or Thinking, Fast and Slow talking about the behavior of an Israeli parole board. Examining over 1,000 decisions, the outcomes for prisoners had more to do with time of day than anything else. Prisoners whose cases were reviewed at 8:50 AM were in great position, whereas those in the mid-to-late afternoon were in much worse position. A prisoner up for parole for the exact same crime would be much less likely to receive it at 4:45 than first thing in the morning.
Rather than anything malicious going on, the parole board was simply worn down mentally over the course of a day. Researchers have attached this story to the emerging understanding of willpower and decision fatigue. The theory is that you have a limited reservoir of willpower—the capacity to make good decisions—that every decision by every person wears down their ability to make good ones. Decision fatigue over the course of a day "can make quarterbacks prone to dubious choices late in the game and CFOs prone to disastrous dalliances late in the evening."
When suffering from decision fatigue, a person will tend to react in one of two ways: 1) to become reckless—acting impulsively rather than to reason through what is necessary to make a good decision—or 2) to shut down and make no decision at all. For the parole board, rather than to do the work late in the day to figure out if they should release potentially dangerous criminals back into the populace, they made the non-decision decision of letting them continue to suffer incarcerated.
Let's assume that it is true that you only have so much willpower and that over the course of making decision after decision any of us is going to deplete the ability to make good ones. How can we use this knowledge to win more games of Magic: The Gathering (especially as applied to big tournaments)?
Five Ways to Win More Games
Force your opponents to make decisions, especially ones they aren't prepared to. It's hard enough to make your own decisions! Now this jerk is demanding I make even more? Every decision you make your opponents make exhausts precious willpower and their limited ability to make good decisions. Because the hallmarks of decision fatigue are poor judgment due to mental shortcuts or "not making a decision at all," I think that you will get the greatest edge here by presenting the opponent with decisions based on valuation, where he has to order two things of similar value or decide how important a seeming-nothing might be.
His reaction will be either reckless or passive; reckless decisions can have dramatic positive outcomes but just as many dramatically poor ones. And when you are forcing the opponent's hand? Passive play is going to be exactly the kind you want to see across the table.
The trick here is to force the opponent's use of willpower without expending too much of your own. That is, decks that force the opponents to do an extra amount of thinking tend to be themselves decision-intensive. This is likely best accomplished by using cards that you can execute on using primarily autopilot resources that your opponents might be less familiar with. In Constructed Magic, forcing creature combat on decks (and their players) who don't particularly want to deal with "blocking" is another (many Constructed decks just want to attack and maybe remove potential blockers).
Creatures and routines that combine these two can be particularly troublesome for opponents, like the first strike-versus-damage redirection (demanding some amount of damage dealt!) on Boros Reckoner, the slow inevitability of combat Cartel Aristocrat, and more-or-less anything involving Werewolves (I can't tell you how many times I've seen a player win a game in Huntmaster of the Fells vs. Huntmaster of the Fells because he just knew the priority timing better than the opponent). Planeswalkers can also fit this bill. Do I attack you or your planeswalker? is a non-trivial question an opponent has to answer that gets even worse when facing multiple planeswalkers.
Practice tying your shoelaces. Tying shoelaces is an interesting example activity for our purposes. Imagine two different people tying their shoelaces. First, imagine yourself; I would guess you can tie your shoelaces in seconds, essentially effortlessly. Though decision fatigue is an emerging field of inquiry (and I am no expert), I would guess that you use little-to-no willpower in tying your shoes.
Now imagine a small child doing the same. My six-year-old can tie his shoes. It might take him a couple of minutes of intense concentration to do so, but he can not only tie his shoes but—gasp—even double-knot them. If you were only evaluating end products, both you and my son can produce a double-tied shoelace (though his might not be as beautifully symmetrical as yours). The differences might be more process and speed and of course the amount of mental energy required. He might squint his eyes and work glacially deliberately so as not to lose grip on the loop in either hand, expending a commensurate amount of willpower as you might when, say, mapping together a particularly harrowing sequence of tiny LEGO.
Clearly two people doing the same thing can require different amounts of precious willpower, ranging from zero to all of a person's focus. A fun variation from the landmark Thinking, Fast and Slow is to actually overload a person's brain by putting a mild tweak on a similar activity.
Find someone who is willing to walk around with you and have a stroll while asking her some simple math questions. 1+1 and 2 x 5 she can probably accomplish without slowing down. Run a couple of those; very likely she will be able to fire those off without accessing any conscious mental energy (nor does walking consume very much). Then lob in something like 88 x 146. Her face might wrinkle up like my son's when tying his shoelaces, and she will stop walking as her brain draws against even the mental energy required to keep walking to answer your question.
The 10-time NCAA champion basketball coach John Wooden taught his players laboriously to tie their shoelaces on the first day of practice. Most new players bristled at this. Why is he teaching me to do something I have known how to do since I was four years old? Wooden had a particular way he wanted players to tie their shoelaces is why! Badly tied shoes lead to blisters, which ultimately keeps men off the court. Fin.
In Magic, there are effective analogues to tying one's shoelaces and practicing tying them. Clearly the same activity can expend close to no willpower or draw all of your willpower focused onto a single activity. I like to think of Patrick Chapin and his favorite kind of deck, Grixis Control. Patrick at various times has compelled teammates like Reid Duke and Jon Finkel to play his multicolor control decks—but he has also often done better than they might have playing the same lists.
While I think that all these very competent in-game decision-makers can get to the same place at the end of a play, that Patrick has spent so much more time on even seemingly acrobatic control decision sets that—while they all end up having to make them—he doesn't burn as much willpower when accomplishing essentially the same thing. This can pay off later in a long day, leaving him more gas in the ego tank to win in a later round.
Choose a simpler deck the less practice time you have. As it is generally true that the more "right" decisions you make, the more value you can build into a game, it necessarily follows that the more decisions you have the opportunity to make, the more opportunities you have to make a mistake. The less you can put on autopilot (due to lack of preparation), the less likely you are going to be able to succeed with a decision-intensive deck even if it is a more powerful option.
Complex decks can produce higher heights of success (and might promise more potential power and wider palettes of options) in part because their many decisions allow for a snowball effect of incremental value, but unless you have enough practice to execute complicated routines on autopilot, You will have to burn substantially more willpower to win even the ho-hum games.
Champion Magic players have produced both beautiful and hideous stories from this angle. At the height of his abilities, winning tournaments and sweeping days left and right with one of the most decision-intensive decks of all time (Survival of the Fittest / Recurring Nightmare) and coming off a US Nationals Top 8 with his signature Forbidian, Jon Finkel decided he only cared about winning (rather than winning and impressing everyone with his deck choice) and made Top 8 of the 1998 World Championship with a stock Deadguy Red, "merely" attacking with Jackal Pups and Wastelands.
From the opposite direction: on the way to winning Grand Prix Columbus with the Billy Moreno Flash-Hulk-Counterbalance deck he had just picked up before the event, Steve Sadin cruised past opponent after opponent just by "flashing" them a look at his assembled combo pieces—until he met future Player of the Year Owen Turtenwald. Owen demanded Steve show him he knew how his combo worked—and he didn't! Despite putting himself in a winning position, Steve had to take the loss against Owen and learn how, you know, the greatest deck of all time actually worked before the next round. Sadin would take Turtenwald down in the rematch in the finals of the Grand Prix, but to be fair it was no drawn-out affair; Steve had the win in his opening hand.
Remember that "complex" doesn't necessarily mean blue or "simple" green. If your deck is going to demand a lot of blocking that means more decisions and if your deck plays cards like Farseek, that means not just more decisions but potentially very telling ones.
Eliminate choices entirely. Closely related to the previous point, you can avoid decision fatigue by avoiding having to ever make potential decisions and classes of decisions in your own game. Please don't think that I am advocating playing decks with lower expected value in the abstract. But if you find a one-color deck with about the same likelihood of winning as a three-color deck (assuming both are played competently), you might want to give a little more psychic weight to the former. All other things held equal, one-color decks demand much less difficult mulligan decisions (you never have to consider shipping a hand that has lands and spells but not the right color of lands).
Here is a crazy one that you might not have thought of but the President practices on a daily basis: he limits what he might wear! If you lay out what you might wear the night before (or say "always" wear your lucky T-shirt / lucky underwear when you play in tournaments), that is one less decision you have to make the day of the tournament.
Eat sugar...and exercise! You already know that in the study of parole officers we cited earlier, potential parolees tended to have better luck early on in the day. Later points and variations in the study showed that you really wanted to be seen at 8:50 AM, while you might have only a 20% chance of parole before the board's morning snack break where judges were served a sandwich and a piece of fruit, that jumped to a brief window of 65% right after.
Running out of willpower doesn't necessarily evince itself in obvious signs of physical fatigue, but an infusion of glucose seems to at least temporarily restore decision-making reservoirs. Glucose seems to be important, as the Times article claimed specifically that "[a]fter performing a lab task requiring self-control, people tend to eat more candy but not other kinds of snacks like salty, fatty potato chips. The mere expectation of having to exert self-control makes people hunger for sweets." Access to snacks over the course of the day can help replenish your willpower during the course of a tournament.
This might seem diametrically opposed to exercise, but I bring it up based on a NASA study. In the last two hours of a workday, non-exercisers drop in efficiency by about 50%, whereas regular exercisers maintain essentially 100% efficiency during those last two hours of the day.
Most of our examples and suggestions here talk about our performance over time—that is, over the course of a day—how your decisions get worse the more decisions you have to make, how you can replenish those reservoirs (at least for a time), or how you can get two hours of efficiency back by exercising. The implication is that these techniques help you not so much to win individual games of Magic (especially early in a day) but to win long tournaments.
Now the prospect of that is quite exciting, don't you think?