A particularly great comment by "Zeid1" on the post "Willpower Isn't Enough"; here's Zeid's comment in full -
The idea of Willpower being the answer is dangerous. An example I think of is 12-step programs for fighting addiction. In almost every 12-step program there is the need to submit to a higher power which can help you stop your habits. This leads to some consternation from those who don't believe in a higher power, but the programs themselves are very effective.
In my view this is hugely due to our cultural idea that the correct way for us to deal with something like addiction is to "Man Up" and will ourselves to stop doing whatever destructive behavior we're trying to avoid. However, in the process of manning up, we're exhausting our ability to continue to do so, and in effect putting ourselves at a prime risk of relapse.
Constant exertion of "will" leads to stress, which is not healthy. Relapse is discouraging. In the end, the result of ending addiction through sheer force of will is a memory of your attempt, which is highly stressful, and ends with failure. This means that if you want to end your addiction later, you will recall your stressful failed attempt, which will then require a larger exertion of "will" to overcome.
It's when you stop trying to will yourself through it that recovery is possible. If instead of directing your life through sheer force of will you instead make small decisions that lead you away from the thing you're avoiding, and you stop trying to force yourself, you will suffer less stress, and when it's time to make those difficult decisions in the face, you will have more "will" to do that.
Our culture assumes that a person's behavior is a measure of their worth, and that the absolute worst thing that can happen to you is that you are not in complete control of yourself. However, there's a loophole in western culture, and that is submission to God. If you let God "guide" you, then you're allowed to let go of some of that control. In the scope of recovery from addiction this would mean you are "allowed" culturally to stop trying to exert your will, and just trust that it will be taken care of for you. But these programs work regardless of the higher power you choose to follow.
What's important though is that you conserve your "will". In my observation and research, when you form habits, you disengage the decision evaluation process that consumes willpower, and the less resistance you put up in general helps you conserve it too. The more stress you need to deal with, the more will it takes to forcibly jump those hurdles, and the more you force yourself to do when your will is exhausted, the more stress you feel. The amount of stress you can tolerate is a limited resource too, and when that runs through, you start supplementing it uncontrollably habits that make you less stressed or more driven, and emotions and anxiety. That's when things can get detrimental, because an addictive substance makes you feel less stressed, or makes you feel more driven, or both. Even though you want to avoid them, your ability to do so is exhausted.
Learning to conserve will has been a huge thing for me. Let my mind do its own thing most of the time, and then I always have the will available to make the important adjustments when necessary, practice the habits that are important to learn, and let problems go without a second though. I try to exhaust myself by the end of the week if I haven't by then, and have a restful weekend. I find it like training a muscle. I want to use it to it's full potential, I want to try and push it a bit further than I'm comfortable, but I want to make sure I can rest and recover. People who try to bully their way through their own life by exerting their will at every turn is like the person who tears a muscle and then tries to lift more weight the next day. The wound doesn't heal, and the muscle gives out.
Peter's example about people who succeed in groups is similar. When we're in a group, you let yourself stop pushing so hard. You can stop forcing things because someone else can take care of something, or someone can remind you of something, or maybe you just feel that someone can do a better job than you anyways. If you put your faith in someone else, you can let go of a lot of stress, if you say "If I can't do it, they can back me up" then you stop worrying about whether you can't do it. In the end, it may be you that does it, but it was because while you were doing it, you weren't worrying about what would happen if you couldn't.
I think what Peter refers to as Inspiration is the same thing as I'd called will. That "inertia" is the product of the memory and anticipation of stress that will be caused by the action. I think that too much exertion leads to failure, which causes stress, which colors your future attitude toward whatever you're trying to do, increasing that inertia. Like the accountability system, you're unable to avoid the habit due to this sort of exhaustion, but going through the process of paying the money takes even more willpower. This leads to remembering how stressful it was to try to avoid the habit, and how disappointing it was to realize that not only did you fail to avoid the habit, you also failed to uphold your promise to punish yourself for doing so. This makes any further attempt to set up a similar system have more "intertia" in the future. But not only that, you've exhausted and stressed yourself out in the process. In some ways, this I think is a good thing, because I think that system is a poor way to do it, so avoiding it is probably in your best interest.
I think these simplified concepts are directly related to more complex biochemical systems, so it totally makes sense that maybe what we think of as exerting will requires hormones to pass from one part of your brain to another, and if those hormones get used up faster than they can put back you will actually have your willpower exhausted, whether you think you should be able to force it otherwise or not.
We can't lift a ton just because we want to. We can't hold our breath for 20 minutes just because we want to. I have no idea why we think we can force our brains to exercise without rest just because we want to. But we can train ourselves to lift more, hold our breath longer, and better control our actions.