Over and over, I have heard writers say that the successful writers are, above all, the most persistent. That staying power is even more important than talent. The ability to keep coming back after rejection, after having a writing project fall apart under your very fingers ... where does that stamina come from?
For me, the writing itself has always been rewarding. Before the world gets a chance to pass judgment, I've already made my own judgments; I've already spent quality time with the manuscript. What keeps you writing?