Mark TWAIN. (№ 10371)

Avoid those who are trying to undermine your faith in yourself. A great man, on the contrary, it inspires the feeling that you can become great.
Another translation:
Stay away from people who scoff at your aspirations. Small people always do that, while the great men always let you feel that you, too, can become great.
Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great.