You are always a valuable, worthwhile human being — not because anybody says so, not because you're successful, not because you make a lot of money — but because you decide to believe it and for no other reason.
If you're not stubborn, you'll give up on experiments too soon. And if you're not flexible, you'll pound your head against the wall and you won't see a different solution to a problem you're trying to solve.
It has done me good, because of the color of the wheat fields. Go and look again at the roses. You will understand now that yours is unique in all the world。