A brief (but outstanding) pearl of wisdom by Carlos Castaneda that I believe really speaks to filmmaking:

A man goes to knowledge as he goes to war, wide awake, with fear, with respect, and with absolute assurance. Going to knowledge or going to war in any other manner is a mistake, and whoever makes it will live to regret his steps.

When a man has fulfilled those four requisites there are no mistakes for which he will have to account; under such conditions his acts lose the blundering quality of a fool’s acts. If such a man fails, or suffers a defeat, he will have lost only a battle, and there will be no pitiful regrets over that.

—Carlos Castaneda