I don't think necessity is the mother of invention. Invention, in my opinion, arises directly from idleness, possibly also from laziness--to save oneself trouble.
There's no agony like [getting started]. You sit in a room, biting pencils, looking at a typewriter, walking about, or casting yourself down on a sofa, feeling you want to cry your head off.
The best time to plan a book is while you're doing the dishes.
