I related in an earlier post a story about Feynman and the necessity of thinking on paper rather than "in the head." Here is another quote to that effect by Anne Enright. She also speaks of "the importance of working more on the page than in your head." But she also emphasizes the necessity of failure. When she hears "of people taking a year off to write, [she] worr[ies] that a year might not be enough. You must fail as a writer for much longer than that."
That failing is often a necessary condition of the possibility of success in any worth while task is often forgotten. That's why writing is not a pleasant activity, but often pure pain (especially when you have a deadline).
It's said that Beckett had a card beside his desk, saying: "Fail. Fail again. Fail better."