[Tinned_Tuna]

"Start viewing willpower as a resource that can be depleted, and make sure you aren’t wasting it on trivial things."

The concept of ego depletion is not as certain as it once was.

http://www.slate.com/articles/health_and_science/cover_story...

[rossdavidh]

The basic idea of "I'm tired, and more likely to make sloppy choices" is pretty well established, however.