This has been a majorly confused phrase of our time. You can’t be yourself if you don’t know who you are in an objective sense: your body/soul, your biology, your metaphysical purpose, your moral status, your abilities, etc. And you don’t know who you are with a mere inventory of your wants and hopes, which are contingent on contexts. The postmodern has deleted human identity and then tells the human to find it, readily creating little boxes to fit you in so they can use your confusion against you. Just “be yourself” is as nonsense as asking a clipped bird to fly. We see the casualties all around us.