When I work with writers in academic settings (see the post "Who do I mean by writers"?), I ask them what they think "Writing" is. Another way to think of this question is "When do you think you are writing?" Like many teacherly questions, it's a leading one, and, in that way, an unfair one: the answer's likely to be one of two things, from the perspective of the person asked. The commonplace answer, the one anyone would expect, and, so, "wrong," or the counterintuitive answer, and so, inauthentic and easily guessed. The latter assumes what one already does is inadequate somehow. The latter lends itself to the skillful feint-- I can guess what you want to hear but don't necessarily believe it myself.
Still, the answer tends to be "I am writing when I am producing pages". So when someone says, "I need to write the first chapter of my dissertation" she may sit down to work believing that she is only "writing" when she is composing words that march towards the right margin, and lines that march toward the bottom of the page, and on to the last punctuation mark. I would like you to consider that everything you do that goes toward the production of the chapter you're working is writing. When you do that, you'll find that you never want for something to do in your allotted writing time. You will be asking yourself questions such as "What can I do today that will move the project forward?"
Much of the time that you'll spend writing will have been spent preparing for the moments when you compose, and that preparation is multi-various and necessary, and even composing itself is not an endpoint, because the process of composing will send you looping back, or in straight lines away from the text, to fill in gaps, produce new plans, add new research, rewrite and revise. The psychologists Bereiter and Scardamalia observed that a mark of the inexperienced writer is that she believes good writers write quickly. But the fact is, good writers plan, structure, revise, rewrite and edit. And while some writers can become adept at producing some texts quickly, that speed is often a mark of experience with a form they've internalized, rather than the the quality of the writing itself.
If you think of the time you spend "writing" as only the time you spend drafting, you'll have a tendency, as well, to take a narrow, perhaps impractical view of drafting, striving for a kind of perfection and speed in production that a particular stage can't tolerate and for which you have not prepared the ground, and you might run yourself into the ground, stalled before you start, or stalled after a quick start.
If you can think of "writing" as all of the steps of "making" that go into the producing the work, you may find that you think more reasonably about each stage of composing itself. That is, you may be more inclined to see the shitty first draft as a necessary step in the process that starts a new phase in the larger process, a phase where you construct a text for others to read.