You know those people who appear to have it figured out?
Granted, they might be on the right path, value-action-alignment, but mostly, they created an environment where they strive in.
You want to be fit and "knowledgable"? Might block your calendar for sports session 4x a week, don't have any candy at home and no TV & WiFi but books.
My guess, just by those 4 changes, that person would be better off and dramatically closers to their ideal state.
So, next time you think about self-control/willpower, rather think about how you can lower the amount of self-control that you need, so you have it in the moments where it's needed and not that you already needed to use it X amount per day and then slip.