"Be yourself" is often said, but it's equally often not actionable advice on its own.

Not everyone knows who or what they are, and even someone who knows is not necessarily able to be themselves without outside help.

I struggle with being myself quite often; there are things I want to do, but I can't simply decide to just do those things... My brain does not work that way. For example, it can take a lot of effort to even say what I truly want to say, because consciously deciding to speak does not necessarily result in me actually doing so, no matter how hard I think the thought.