“Just be yourself”

is solid enough advice if it is given divorced from external outcomes. Because, yes, it will be hard to ever be internally tranquil if your social persona is critically divergent from your “true self.” But out in the world, no, “being yourself” guarantees you nothing. Maybe you come across as more “authentic” or “at ease.” So? That doesn’t mean any external problems will be solved by you really being you. What if your “true self” sucks? Is super weird? Cares about things society ignores? Ignores markers society deeply values? 

What is true here is probably true for many bits of cliche advice: if you only want to follow the wisdom because you think it will get you something, the wisdom won’t prove all that wise.