I've noticed two dangerous extremes that I have fallen into at various points in my life: diving in and writing without a plan or any forethought (leading to two handwritten manuscripts of about 3,000 and 6,000 words that I abruptly abandoned when I realized that both of them weren't going anywhere because I'd made my protagonist too-obviously invincible), and planning and planning at such great length that I never get down to actually writing. (The latter is the danger I need to be wary of now; both the scope of my Shine Cycle and my training as a technical writer have hammered home to me how important it is to plan before writing.)
Going back in the middle of a draft to revise before finishing is something that pretty much every book on writing I've read (that isn't obviously wrong on pretty much every point---a caveat I have to add now that I've read one arguing that planning of any sort is always a waste of time) has recommended avoiding, because you'll tend to keep revising and revising and never finish the draft.
Heinlein was famous for never revising (his short stories, at least; I don't know about his novels) unless an editor asked him to make specific changes. But while I think every author would like to be able to write salable stories in one draft every time, and it's a goal that's worth striving for, very few of us are that good yet.
