Perseverance. That's what it takes to be a writer. You keep on finding the ideas, pushing them into a write-able shape. You work at the first draft until it's finished. You take out the red pen and push through the re-write, then you keep on polishing and honing until you have a book that you're happy to submit. Phew - I'm exhausted writing about all that perseverance.
In his article, Writing Is Worth It, Simon P Clark writes about this issue from his point of view. It's well worth a read of this post on the Writers & Artists website. Have a look.