This seems right to me

"So much in writing depends on the superficiality of one's days. One may be preoccupied with shopping and income tax returns and chance conversations, but the stream of the unconscious continues to flow undisturbed, solving problems, planning ahead: one sits down sterile and dispirited at the desk, and suddenly the words come as though from the air: the situations that seemed blocked in a hopeless impasse move forward: the work has been done while one has slept or shopped or talked with friends." --Graham Greene, The End of the Affair

Well, maybe not 100% correct, but close.