When an art show sells out the first night of the show, well that is big success, right? I think that is wrong. Success does not depend on others agreeing with you that you are good and that is what selling out is all about. Everybody wants to get something that is seeming to be a hot item. Then after that happens everybody treats you differently, as though you are amazing and your work is way way better than everyone else that did not sell out the first night. That is the way the world works.
But the artist should not be a part of that thinking or you will be ruined. An artist should not care what happens to his work. His job is do the work that only he can do and let the chips fall where they will. The artist is successful if and only if he does all he can to be the best unique artist he is. Only you know if you are successful or not. You are not better or worse because somebody else did or did not like your work enough to buy it. If you know this you will be free.
Never let someone else tell you what you are. That is between you and God.