“Be yourself” + “Give yourself time to grow” + “You can be anything you set your mind to” are not contradictory and indeed need to all be taken together. I suppose a less kind to put it is “Authentically and gradually shape yourself into a person of your own choosing. We are all going to presume you’ll pick well in either a prosocial or profitable sense. If you don’t shape yourself well then it will be unpleasant for everyone especially you.”