Did you know that Madeleine L'Engle almost gave up writing when she turned 40 after getting yet another rejection notice? "With all the hours I spent writing, I was still not pulling my own weight financially." She discovered, however, that her subconscious wouldn't let her NOT write. 

"I had to write. I had no choice in the matter. It was not up to me to say I would stop because I could not. It didn't matter how small or inadequate my talent. If I never had another book published, and it was very clear to me that this was a real possibility, I still had to go on writing." (Source)