Tldr: There is no 'you.' You are always in a state of becoming. Instead of 'just being yourself',' be the sort of guy who succeeds and achieves what  you desire. Be the person you want to become.

There is no intrinsic 'you.' Unless you are 100% autistic, how you present yourself varies according to the situation. The way you act around your boss, friends, parents, girls, etc should be different if you have the slightest amount of social and emotional intelligence.

Moreover, those core interests and identities you have right now will be no more the same 7 years from now as the were 7 years ago. Who 'you' are will change. That is inevitable. The question is, will it be positive or negative: a rapid ascent of compounded daily and hourly 1%  improvements, or the pathetic gradual decline of someone who dug into the behaviors and characteristics that were getting them nowhere.

It all goes back to the old, wise Native America parable. It's said, inside each person are two wolves fighting for dominance: one representing the negative, self-destructive side; and another representing one's positive, growth-oriented side. The one that wins is the one each person feeds the most on both a monetary and crucial basis.

I don't think there's ever been a successful person in any endeavor who got by by just 'being themselves,' who didn't actively and effective combat their weaker selves until they were remade anew and better.

Usually, when people say, 'just be yourself',' they mean, on some level, don't cower in the face of inter-personal pressure. This is absolutely the case. You should have a strong frame and personality, but it should also be one that you are consciously practicing as the best version of yourself in different relevant situations.

So don't be 'yourself.' Instead, decide what you want and become the sort of person capable of achieving it.