All of Baumeister’s research suggests self-control is a strenuous act. As your ego depletes, your automatic processes get louder, and each successive attempt to take control of your impulses is less successful than the last…Inhibiting and redirecting your own behavior in any way makes it more difficult to delay gratification and persevere in the face of adversity or boredom in the future…

The current understanding of this is that all brain functions require fuel, but the executive functions seem to require the most. Or, if you prefer, the executive branch of the mind has the most expensive operating costs. Studies show that when low on glucose, those executive functions suffer, and the result is a state of mind called ego depletion…The early psychologists would have said when your ego is weak, your id runs amok. We now know it may just be your prefrontal cortex dealing with a lack of glucose.

Remember, no matter what the self-help books say, the research suggests that willpower isn’t a skill. If it was, there would be some consistency from one task to the next. Instead, every time you exert control over the giant system that is you, that control gets weaker. If you hold back laughter in a church or classroom, every subsequent silly notion is that much funnier until you run the risk of bursting into snorts.