Junot Diaz has an excellent short essay in Oprah Magazine about the trials and tribulations of writing The Brief Wondrous Life of Oscar Wao for ten years:
That's my tale in a nutshell. Not the tale of how I came to write my novel but rather of how I became a writer. Because, in truth, I didn't become a writer the first time I put pen to paper or when I finished my first book (easy) or my second one (hard). You see, in my view a writer is a writer not because she writes well and easily, because she has amazing talent, because everything she does is golden. In my view a writer is a writer because even when there is no hope, even when nothing you do shows any sign of promise, you keep writing anyway. Wasn't until that night when I was faced with all those lousy pages that I realized, really realized, what it was exactly that I am.