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.
One of the greatest challenges many writers face is discouragement. And some of the most painful discouragement comes in the form of negativity from people when you talk about what you're doing with your writing. Even well-meaning friends and family members can take the wind out of our sails with questions and comments like "Is there really any money in that?" or "So, I went to Barnes and Noble, but they said they didn't have anything by you..."
Maybe you can't (or shouldn't) truly "keep away" from those people. After all, we all have our flaws. But you can try to keep their words away from your mind and heart. Seek out the people -- writers and non-writers -- who are encouraging and supportive. Let their words be the ones that take root within you.