You don't have to be 100% certain about anything to be
   successful. You can act *as-if* something is true without
   necessarily believing it completely, and then seeing what
   happens. It is like one of my favorite sayings: "Be Brave.* If
   you cannot be brave, *act brave*: No one will know the
   difference." Doubt is ok. Doubt is normal. But if doubt is
   holding you back, act as if you were someone who was certain.*
   You'll still get there.