I like this interview of Stephen King (who I think is a hell of a good writer) by Neil Gaiman (one of my favorite authors). Here's a part of the interview that especially resonated with me:
“I never think of stories as made things; I think of them as found things. As if you pull them out of the ground, and you just pick them up. Someone once told me that that was me low-balling my own creativity. That might or might not be the case. But still, on the story I am working on now, I do have some unresolved problem. It doesn’t keep me awake at nights. I feel like when it comes down, it will be there...”
King writes every day. If he doesn't write he's not happy. If he writes, the world is a good place. So he writes. It's that simple.