My experience is that who you truly are develops and becomes clear through time.

You sound young, is this so? If so I think finding out who you are is entirely usual. Even then, there’s developments and adjustments along the way, and we might find ourselves not who we were initially, mid life is often one such adjustment.

So say you did take up running in order to please others, right now that might mean you are the kind of person who cares deeply about others perception of them. But it could be you are currently evolving, questioning your previous needs to be accepted/admired. You could be finding out that you prefer to seek fulfilment in other ways which may or may not involve running.

I may be offbeat here but the above are my own thoughts about self identity.