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.

Source: MacLaren, Gay. Morally We Roll Along. Boston: Little, Brown and Company, 1938. Additional Information: While this quote is commonly attributed to Mark Twain, it does not appear in any of his writings or speeches. Rather, the saying and attribution are based on elocutionist Gay Zenola MacLaren's recounting of a childhood encounter with Twain. MacLaren wrote the following, which would become the basis of this popular quote and attribution, in her 1938 memoir:

[Twain] opened the door for me himself. As we said good-bye, he put his fingers lightly under my chin and lifted my head up so that my eyes met his.

“Little girl,” he said earnestly, “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.”