Decisions tire the brain. In a famous study, Israeli parole judges were more likely to grant parole early in the day (70 percent) and almost never late in the day (less than 10 percent) after controlling for all other factors.

Psychologists call this “decision fatigue.” Every decision we make weakens the brain’s capacity for reasoning and paying attention. Only a full night’s sleep restores our maximum capacity, but bursts of sugar (glucose in the blood) will temporarily alleviate the condition.

Knowing this information obligates us to design around it. How often, for example, do you attend all-day meetings that end with critical decisions? Scheduling day-long meetings with decisions at the end all but guarantees weak outcomes. Tired participants tend to give in to the most vocal participant or to accept the defaults, like the parole judges.

When I designed a two-day persuasive design lab, I intentionally designed it as two half days. Because the most important decisions are made on day two, I try to hold the second session from 9 a.m. to 1 p.m. with lunch arriving at noon. We make final decisions on pilot plans after eating.

I use a personal strategy to minimize the effect of decision fatigue, too: personal policies. I borrowed the idea from Daniel Kahneman’s book Thinking, Fast and Slow. He talks about risk policies, like never buying extended warranties. By adopting a policy, I don’t have to decide every time a situation arises.

Here just three of my personal policies:

* Never switch to an earlier flight on the day of travel * Never buy extended warranties * Always wear a black t-shirt, khakis or jeans with no belt, and slip-on shoes when traveling

Maybe it sounds silly, but these policies save me from the agony of deciding and from the unexpected calamities associated with airline travel decisions. (I once switched to an earlier flight, got bumped from that flight, and missed my original flight because of problems re-ticketing.)

If you want to keep your brain rested for important decisions, apply these three tricks:

* Create personal policies to set defaults for trivial matters * Assign important decisions to early in the morning * Split full-day meetings into two days, with the big decisions the morning of day two

For more on Decision Fatigue, see this NYTimes story. And share your personal policies in the comments below.