"Just Be Yourself" is the commonest phrase delivered gift-wrapped as advice for free by people to the needful who are too anxious to ask for or pay heed to any sort of advice.
Be yourself, don't stress, just act normal. Isn't the stressed out, abnormal behaviour a part of the person's personality. How can one teach someone to be oneself? No one knows me better than me myself. If I act in a pressure situation in a certain absurd way, am I not being myself?
Or perhaps what they mean is that one should act as one would had there not been any stimulus of pressure or stress situation. But then, isn't that acting abnormally? Acting like everything is fine when it is not?
I think we should abolish the phrase "just be yourself", instead use "just pretend as if nothing happened. Blindfold yourself and jump into the well with a smile." But then it would be a very long phrase for common usage. Anyway, till I get the changes done, you can continue to be yourself.