How Do You Manage Self Doubt?

I was surprised to hear that you have a depressive tendency because so much of your work seems so buoyed by light. Do you still have Self Doubt? I mean I've read... I think I heard actually on 60 minutes that you feel like you're paid for your confidence and decision making. There's definitely room for Self Doubt. The purpose of it is to know what you're doubting. So the Self Doubt can come when you get past what you think.