One of my favorite themes/topics/contemplations is habits. How to build, change, and break them. I had not though of the relationship between habits and will power.
This is helpful to see the dynamics between the two aspects. What does work for me is if I break down the steps in changing a habit into tiny tiny tiny steps.
If I plan to add exercise to my routing, I pick a time that works for a short exercise and begin by thinking about the exercise and then sitting for that period of time and then a few days later when I have set the time for doing the exercise, I start actually doing it.