You grow a whole lot more as a writer by getting old stories out of the house and letting new ones come in and live with you until they grow up and are ready to go. Don't let the old ones stay there and grow fat and cranky and eat all the food out of the refrigerator. You have dozens of generations of stories inside you, but the only way to make room for the new ones is to write the old ones and mail them off.

How to Write Science Fiction and Fantasy (ed. Writers Digest Books, 1990)