Does your Desire system lead you to unhealthy things?
If so, that's challenging. This is because your desire system has a unique power: it focuses your attention on anything that releases dopamine. If that happens to be something like cigarettes, that causes problems.
The same power of Desire
The good news: hanging out with a loved one, eating healthy food, and any task important for survival also releases dopamine. In fact, everything that is healthy also releases dopamine.
The difference between an Unhealthy and a Healthy Lifestyle
The difference isn't willpower. The difference is where you get your dopamine from. Or, in more concrete terms, the difference is what you spend your time focusing on and thinking about.