From Brooklyn Follies by Paul Auster:
There were no rules when it came to writing, he said. Take a close look at the lives of poets and novelists, and what you wound up with was unalloyed chaos, an infinite jumble of exceptions. That was because writing was a disease, Tom continued, what you might call an infection or influenza of the spirit, and therefore it could strike anyone at any time. The young and the old, the strong and the weak, the drunk and the sober, the sane and the insane. Scan the roster of the giants and semigiants, and you would discover writers who embraced every sexual proclivity, every political bent, and every human attribute—from the loftiest idealism to the most insidious corruption. They were criminals and lawyers, spies and doctors, soldiers and spinsters, travellers and shut-ins.
“Joyce wrote three novels,” Tom said. “Balzac wrote ninety. Does it make a difference to us now?”
“Not to me,” I said.
“Kafka wrote his first story in one night. Stendhal wrote The Charterhouse of Parma in forty-nine days. Melville wrote Moby Dick in sixteen months. Flaubert spent five years on Madame Bovary. Musil worked for eighteen years on The Man Without Qualities and died before he could finish. Do we care about any of that now?”
The question didn’t seem to call for a response.
nilanjana s roy 
I’m reminded of one of Michael Cunningham’s interviews, where he talks about teaching Fiction Writing to his students at Brooklyn College. He said,’I’m always very sure to include William Gass’s “In the Heart of the Heart of the Country,” which is probably the best example I know of an entirely successful, and I think great story, that breaks every single possible rule about writing. Part of what I’m trying to talk to them about is the fact that, as far as we can tell, there are certain principles by which fiction seems to work, and yet anything that’s put forward as a principle for writing fiction has been dramatically contradicted by at least one great work of art. So we find ourselves in the funny position of having rules as vague guidelines and yet nothing, not one thing, that we can count on. And William Gass is very good for that.’One of the rules, I guess, is to be able to reinvent oneself from book to book. (Else, one day you might find yourself published by The Factory, a new publishing house that’s part of Ramu’s Vision 2020.) Ironically though, Auster himself, stuck in the trench of Chance, has failed to do so. And so has your home-bred austeremulator Raj Kamal Jha.