Writers don't write, I was repeatedly told at my first magazine job in New York, they rewrite.
Every time I heard it I wanted to weep.
And I didn't believe it. Every time I did have to rewrite something, I took it as a sign that I wasn't really very good at this, and that I should start looking for a more suitable line of work at my earliest opportunity.
Truth be told, I still think that what flows from my keyboard should be so pristine that it allows for no further improvement. To this day I can't understand why it's not…but at least, in a small sign of progress, I do understand that it's not.
Writing is a process—of discovery, of refinement, of invention.
The notion that you can just bang it out in immaculate condition is worse than arrogant, it's positively self-destructive. First of all, you'll give yourself a complex thinking that all the other writers out there are turning out perfect prose while you're not. And second, you'll fail to do what needs to be done to make your work as good as it could, and should, be.
William Faulkner, in an oft-quoted remark, said, "You've got to kill all your darlings," and while I think that may be a bit of an overstatement—surely some of your darlings can be spared—I take his general point. You have to be ruthless in the service of the work. Many times the very thing that sparked your imagination, that got you writing this particular piece in the first place, will turn out to be, by the time you're done, irrelevant of beside the point. There's even a chance that it will have been superseded by something better, more apposite, which only occurred to you while writing. Most good things occur to you not while you're thinking about writing but while you're actually doing it. This is something that legions of would-be writers never grasp; they claim that they've composed entire stories, novels, and clever essays but that so far, tapping their foreheads with one finger, the pages are all still "up here." It's just a matter of finding the time, they say, to put everything down on paper. (Only they never get around to doing it, do they?)
Great writing is seldom written; it's rewritten, and yes, the ink is usually diluted with blood, sweat, tears, and way too much Diet Coke.