Comment: Re:And... (Score 4, Informative) 484
I couldn't find the study earlier, but here is a pretty good writeup of the effect:
http://www.nytimes.com/2011/08/21/magazine/do-you-suffer-from-decision-fatigue.html?pagewanted=all
"Willpower turned out to be more than a folk concept or a metaphor. It really was a form of mental energy that could be exhausted. The experiments confirmed the 19th-century notion of willpower being like a muscle that was fatigued with use, a force that could be conserved by avoiding temptation."
I don't disagree that regular exercise of willpower can have positive effects, though.