Fear is the mind-killer.

I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.

– Frank Herbert, Dune

http://www.goodreads.com/quotes/2-i-must-not-fear-fear-is-the-mind-killer-fear-is