Some people say to write down everything and only edit later. I take the opposite tack. I used to believe that I rarely edited at all because I usually publish something as soon as it's done. Then a friend watching me write said that she was getting seasick from my tendency to go back and forth deleting and rewriting the same sentence fragment or paragraph before moving on. Most likely the best writers combine both editing methods.

In the past, only the "edit later" method was even possible, because word processors didn't exist yet. There's really no longer any such thing as a "first draft" because we now tend to revise continuously instead of discretely.