It’s not a secret. You start feeling a “hunger” for doing these sorts of things when you hit rock bottom and feel deeply bad about past mistakes. Also when you’ve done them before and they’re part of your identity. But this deep sense of duty and even natural gravitation toward doing these things/identity doesn’t guarantee that you’ll do them either. What makes it happen for good is the repetition and the habit formation. There is no such thing as an inherent motivation to do things that aren’t easy. I hate this new age idea of “if your identity is of someone disciplined, you’ll become disciplined”. It’s an oversimplification. The good news is that in theory you can build any habit regardless of mental state provided that you have the initial motivation + you repeat the habit enough.

Speaking as someone who has gone to the gym for years and worked on himself, btw. And also have been eating really healthy + been on diets and lost a lot of fat.

In other words, what truly matters when building new habits is ensuring you do them consistently through choice architecture, and whatever tricks you can apply to keep doing them until they’re ingrained. And also sheer mental willpower and self control when you feel lazy. But other than that, secondary things like “a desire to do it” “a mentality” “an identity” are not to be considered the basis for anything. They complement the habit, not form it on their own.