French writer Gustave Flaubert was notorious for the slowness of his writing, agonizing, it seems, for hours over the word choice of a single phrase. That always comes as a surprise to me when I think of it, for he was not a concise writer. In fact, his novels are often tediously lengthy and full of minute descriptions, a style that would go out of fashion when the new-fangled technology of photography could do it better.
My advice to my writing students and the writers is coach is just the opposite: draft fast and rewrite slow. Whether it's a term paper, a short story, a self-help book, or a novel, getting as much down to work with as quickly as possible keeps your brain going and the words flowing onto the page. You get all the ingredients down into this "zero" draft, this predraft, and then you can go back and fill in the gaps, flesh out the characters and the dialog and the description or the argument.
Drafting fast is a great way to get past writer's block. Writer's block is seldom about a lack of ideas; it's much more often about a lack of faith: faith in the writer's ability, faith in the saleability of a piece. So drafting fast, not caring about the tidiness or the grammar or the success of this initial go-round can break through that resistance. After all, this isn't even the first draft, it's the zero draft.
And the zero draft never has to start at the beginning. It can start at the end or in the middle or wherever you have some strong sense of what you want to say. A beginning can be added on later; in fact, everything can be rearranged, reworked, rewritten. It's just a place to start and a good one at that.