There's not such thing as a permanent fixed identity though. "Just be yourself" raises a more interesting question. Who is yourself? Why is that way? Why should it be that way? Have you reflected on why you want what you want or why you behave the way you do? Do you think the way you are is the way you should be? Or is there a cognitive disconnect between the is and ought?

This is 100% true, which is why it's so important to resist the societal pressure to conform. It might be tempting to avoid these questions by taking the "default" path, but that path is unlikely to lead to happiness. You have to decide on your own path and work to make it happen.