There is a very perceptive essay by Susan Sontag, called "Directions: Write, Read, Rewrite. Repeat Steps 2 and 3 as Needed." Apparently, it first appeared in the New York Times.  It is mainly concerned with the writing of novels, but it appears to me that what she says applies to almost all kinds of writing.
Most interesting (and true) is how she connects the acts of reading and writing. She thinks that "to write is to practice with particular intensity and attentiveness, the art of reading. You write in order to read what you have written and see if it's OK and, since of course it never is, to rewrite it—once, twice, as many times as it takes to get it to something you can bear to read" (223). This is probably the most important difference between a serious writer and a scribbler like myself: "as many times as it takes to get something that [I] can bear to read" usually does not go beyond twice. Clearly, Sontag was her "own first, maybe severest reader." She thought that she was actually following Ibsen's maxim that "to write is to sit in judgment of oneself," most of us don't, even though we all would find it "hard to imagine writing without rereading"—at least once (223).
Sontag is, of course, not the only writer who thought that revision is where it's at. Just three other examples: “First drafts are for learning what your novel or story is about” (Bernard Malamud). “There is no great writing, only great rewriting” (Louis Brandeis). “Books aren’t written—they’re rewritten. Including your own. It is one of the hardest things to accept, especially after the seventh rewrite hasn’t quite done it” (Michael Crichton). I do find, however, that Sontag's phenomenological description of the writing process is more precise, just because she calls attention to the activity of reading and rereading as central in revision.
"Reading usually precedes writing" (226). The reading for the writing of non-fiction includes note-taking, paraphrasing and summarizing. It's very different from the reading of novels she describes, in which there is a "complete elimination of the ego" (Virginia Woolf). Disembodied rapture is not what is needed here, but critical understanding and evaluation. Some would argue that the same holds for novels—at least sometimes. And I would suppose that Sontag would agree.
Furthermore, writing for me is similar to writing for her in that "what I write about is other than me. And what I write is [usually] smarter than I am. Because I rewrite it. My books know what I once knew—fitfully, intermittently" (228). But not always and not reliably, if only because I may not have reread and rewritten it sufficiently many times.  This also makes for the accumulation of "uncertainties and anxieties" she notes as essential in writing.
See also Husserl on Writing and Thinking
1. I read it in the version that appears in Writers on Writing, Collected Essays from New York Times. Introduction by John Darnton. New York: Henry Holt and Company, 2001 pp. 223-229. One of the annoying things about this "edition" is that it does not give any indication as to when the original essays appeared.
2. As a massive disclaimer let me point out that these blog entries should be viewed more as notes to myself than as finished products.