A man is a fool not to put everything he has, at any given moment, into what he is creating. You're there now doing the thing on paper. You're not killing the goose, you're just producing an egg. So I don't worry about inspiration, or anything like that. It's a matter of just sitting down and working. I have never had the problem of a writing block. I've heard about it. I've felt reluctant to write on some days, for whole weeks, or sometimes even longer. I'd much rather go fishing, for example, or go sharpen pencils, or go swimming, or what not. But, later, coming back and reading what I have produced, I am unable to detect the difference between what came easily and when I had to sit down and say, "Well, now it's writing time and now I'll write." There's no difference on paper between the two.
— Frank Herbert
(Via Scott McAllister while he was off on a crazy Dune research kick)