Thanks for the quality comment. It really is difficult to define since the sense of self is just a concept to begin with.
By being yourself, I would take that to mean being true to your intentions, interests, and general demeanor in the moment. All those can change with time.
Avoiding things like pretending to be interested in sports, pretending to hate comics, pretending to be a “player”, pretending to be overly macho, hiding politics, etc are all things that I have seen people do. If your interests change that’s normal but I wouldn’t recommend feigning things that are untrue for you in the moment.
I think aspiring for self improvement would still count as being true to yourself if you genuinely want to improve.