Unfortunately most people who quote that are weak and boring people who are incapable of the intensity required of someone who tries to live with that philosophy. Here is another very famous section of the book. The Bene Gesserit Littainy against Fear. Pg 19 of Dune 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.