"Researchers say we humans have a limited supply of willpower" -- it's an interesting idea but worth noting there are counter-claims.

Particularly, it turns out that this may be self-fulfilling prophecy -- people who subscribe to the limited willpower hypothesis tend to run out of willpower more quickly[1]

What's interesting here, for those looking to practically increase their willpower, is that treating your willpower as delicate and fundamentally limited might be part of the problem.

Personally, I'd like to subscribe to the 'abundant willpower' hypothesis, if that turns out to be the more powerful premise. (But then, I'd also like some cake. What can you do? ;) )

[1] http://www.livescience.com/38980-willpower-is-not-a-finite-r...