Who are you?

Got an email yesterday from a long term friend of mine. In it he talked about questioning himself. Got me thinking about the times I've questioned my identity, the times iv'e struggled with who I am and what I stand for. Guess the root is in who sets your identity for you? Do you base your view on yourself on what others say about you, what you see yourself as or on an external source's view of you (e.g. Bible)?