But what's the explanation for people to go low on willpower after exerting willpower?
My reading of the passage Kaj_Sotala quoted is that the brain is decreasingly likely to encourage exerting will toward a thing the longer it goes without reward. In a somewhat meta way, that could be seen as will power as a depletable resource, but the reward need not adjust glucose levels directly.
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.