Willpower: Rediscovering the Greatest Human Strength
by Roy F. Baumeister and John Tierney, 2011

Highly recommended. Gives tips on why you are so cranky at the end of the day. Hint: willpower depletion and decision fatigue. You have a finite supply of willpower, and it won’t be replenished without food or sleep. The book has useful long-term strategies on how to conserve willpower by creating routines, setting plans with to-do lists, and creating if-then rules for eating, drinking, and behaving. Relatively quick read, with lots of references to behavioral research.