"That's why I make a point of never showing pictures I'm working on to anybody because if a person likes it too much, I'm disturbed and if a person doesn't like it, I am also disturbed, because somehow that will freeze it and I wouldn't dare go on with it. Either I want to destroy it or else I think it's so good that I don't want to touch it. And that's the beginning of the end."
--Andrew Wyeth, in Two Worlds of Andrew Wyeth: Kuerners and Olsons, Metropolitan Museum of Art
He was a painter. But this can apply to many kinds of artists.