You have never seen your own face directly, only versions returned by something else.

Everything you know about your own face has come back to you through glass, glass reversed, or a lens. Every other person has looked at you directly and you never have. This is a small, permanent asymmetry in a life otherwise built on the assumption that you have the best view of yourself.

Extend it a little further. There are things about how you come across that others perceive directly and you receive only in reflections, if at all. Asking someone honest what you are like to be around is the closest available equivalent, and it is worth doing once in a while.