Some stories are born from the inspiration that can come only from a muse--others from the demons that stalk the imagination. It all depends on which is crying louder at the time.
There are storytellers that latch onto one or the other, spending an entire career praising some idealistic creature that has crossed their path, infusing all their prose with the beauty of a single face. Some chose to side exclusively with their demon, allowing themselves to be dragged down for the sake of that truly magical story that needs the darkness in order to see it through.
Sometimes, I'm not so sure they aren't one in the same.