I think you're totally missing the point. The point is that most of your actual lived life is simply stimulus and response. We actually have an extremely limited capacity for making reasoned choices - we just don't have the mental energy. So instead we learn to respond in a certain way to a certain stimulus (habit).

Here's an example from my life: I used to go the gym every Wednesday night after work. Several times over the course of this habit, I realized at the end of a long day that I would be better off going home and getting some rest, and decided to go home instead. In nearly every single instance I still drove to the gym, even though I had decided to go home. Because I was on auto-pilot. If we're talking about willpower, I would have say that it was my lack of willpower that led me to going to the gym and working out that day.