'Who you are' is one and the same with 'why you are'; the two can never be separated! It is clear then that you don't determine or define yourself, you discover yourself.
No man can tell you whether you are successful or not; you are your own judge on the matter. If you need another person to tell you whether or not you've been successful, then that success is hollow and empty. True personal success is a subjective experience that can only be validated by a deep and abiding inner joy and happiness within you.