The fellow who has not had any experience is so dumb he doesn't know a thing can't be done, and he goes ahead and does it (Charles F. Kettering).
The person who says it cannot be done should not interrupt the person doing it. (Chinese Proverb).
You have to allow a certain amount of time in which you are doing nothing in order to have things occur to you, to let your mind think. (Mortimer Adler).