Some really smart writer said it best: Writing is rewriting. The quote is often attributed to Ernest Hemingway, but a whole lot of writers say the same thing. You need to get the first draft down, and maybe the second and the third, etc., and then the real work begins.
Ah, if only it were that simple. My process is a bit more complicated, because my internal editor is a FEROCIOUS PIRATE! ARRGHHH!