[krageon]

I'm not hand waving it, I literally did it. It is not easy but also not some terrifying abyss. I think in such scenarios it doesn't help people to present this as a really big problem, they are helped with the reality: It is something to do if you want to do it. If you do want to, you can. It doesn't require a significant lifestyle change, just regular exercise time (even once a week makes a big difference in most people). It's effort and it's not fair, but it is eminently available to almost everyone.

Edit: I'm sorry, I glossed over the "force of personality" part. This might take you a few years to get right, but since it boils down to "be more assertive" the only way to get better is to consciously work at doing it. It is the same as building any other habit.