Lots of truth in this although I think you perhaps underestimate the role of interests and personality traits. I’m physically lazy by nature and absolutely loathe strength training, which I have tried in many different forms and for many years. I’m great at other stuff like language learning for example which I find fun and rewarding, even if it also takes a bit of discipline. I have a friend who is a real gym rat with an enviable body, he loves going to the gym and feels good when exercising (but only speaks one language to my knowledge and has no interest in language learning). From the outside it may seem as he is sacrificing more than me when it comes to strength training but knowing how it looks ”from the inside” a more important factor is that he simply enjoya strength training, while I don’t (hence what looks like a big sacrifice to him isn’t one, just as my intense language studies isn’t a big sacrifice for me).

The people who become great at various things are often disciplined etc but it helps if you like what you’re doing. If you hate it, there is almost no way you can discipline yourself to become good at it and you may just as well find something else to get good at - at least that’s my experience.

Merry Christmas!