I really recommend you check out this New York Times article on willpower . Excerpt:
"The brain has a limited capacity for self-regulation, so exerting willpower in one area often leads to backsliding in others. The good news, however, is that practice increases willpower capacity, so that in the long run, buying less now may improve our ability to achieve future goals — like losing those 10 pounds we gained when we weren’t out shopping.
"The brain’s store of willpower is depleted when people control their thoughts, feelings or impulses, or when they modify their behavior in pursuit of goals. Psychologist Roy Baumeister and others have found that people who successfully accomplish one task requiring self-control are less persistent on a second, seemingly unrelated task...
"Other activities that deplete willpower include resisting food or drink, suppressing emotional responses, restraining aggressive or sexual impulses, taking exams and trying to impress someone. Task persistence is also reduced when people are stressed or tired from exertion or lack of sleep."
And here's your homework:
"In the short term, you should spend your limited willpower budget wisely. For example, if you do not want to drink too much at a party, then on the way to the festivities, you should not deplete your willpower by window shopping for items you cannot afford. Taking an alternative route to avoid passing the store would be a better strategy.
"On the other hand, if you need to study for a big exam, it might be smart to let the housecleaning slide to conserve your willpower for the more important job. (YES! - Hillary) Similarly, it can be counterproductive to work toward multiple goals at the same time if your willpower cannot cover all the efforts that are required. Concentrating your effort on one or at most a few goals at a time increases the odds of success...
"In psychological studies, even something as simple as using your nondominant hand to brush your teeth for two weeks can increase willpower capacity. People who stick to an exercise program for two months report reducing their impulsive spending, junk food intake, alcohol use and smoking. They also study more, watch less television and do more housework. Other forms of willpower training, like money-management classes, work as well."