Kenny sent around a New York Times article on scientific studies of willpower capacity, which basically established that we have a finite capacity of willpower that can be exhausted, but that the capacity for greater willpower can be developed over time, mostly by practice. Personal willpower is a theme that often comes up in the SKS, since it's a necessary-but-not-sufficient capacity for nearly all forms of success, including spiritual success.
A few other observations on the article's ramifications:
Given that our capacity for willpower can be exhausted, it would stand to reason that virtue requires not so much a greater capacity for willpower, so much as the wisdom to avoid temptation. Achieving any great goal usually requires revising your lifestyle, and the overall context in which you function, in order to minimize the temptations and distractions. If you want to quit smoking, the first thing you need to do is stop hanging around other smokers. If you want to study a lot, cultivate relationships with people who hang out at the library instead of the bars. Augie Turak and many other spiritual teachers maintain that this insight can be extended into every aspect of your life, until everything you do, no matter how mundane or innocuous, is geared towards cultivating the kind of life you want.
If controlling your "cognitive environment" is the key to maximizing the value of your willpower, then it also stands to reason that you ought to limit, or at least carefully control, your media intake. Commercial media are doing their darnedest to wear out your willpower to get you to buy things. They understand that if they just keep wearing you down, they can eventually get you to buy more stuff. When you watch TV, you are giving someone else complete power to pour images and ideas into your brain, with almost no time to filter, digest, or reflect upon them.
"Lead me not into temptation" would be especially important if you are trying to maintain a standard for sexual behavior. The whole "just say no" abstinence campaign is practically useless if the kids are put in situations that force them to "just say no" so often that their willpower is eventually exhausted. In his book Predictably Irrational, Dan Arily cites his research that people consistently and vastly underestimate how weakened their willpower will be when they are impassioned . . . which is why so many otherwise rational people wind up doing things they deeply regret in the morning. Rather than telling young people the right thing to do, and then consistently putting people in situations where they will be tempted not to, let's just constraint temptation to begin with. All those "repressive" things we had back in the 1950s â€“ dress codes to enforce modesty, gender-segregated schools and classrooms, curfews, chaperons, etc. â€“ are now justified by scientific evidence as sensible means to achieve a desired end.
I think the key to all willpower is not willpower at all, but consciousness â€“ an awareness of what you're doing and why you're doing it. You can't exert your willpower until you become aware of the circumstances in which willpower is called for. Once you've cultivated that capacity for self-consciousness, it can carry over into many other spheres as well . . . which is why, as Kenny pointed out, it gets a lot easier to brush your teeth twice a day if you're exercising regularly as well.