> “Willpower”is filled with advice about what to do with your willpower. Build up its strength, the authors suggest, with small but regular exercises, like tidiness and good posture. Don’t try to tame every bad habit at once.

This is the key. For example, instead of having a bunch of New Year's resolutions, come up with one resolution every month. Focus your (finite) willpower on making it into a habit, at which point it won't require willpower anymore. Next month, move onto another habit and do the same thing. You can drastically change your lifestyle in just 1 year by repeating this 12 times.