Suppose that your home was a mess and you had one hour before a visitor arrived--a visitor that you wished very much to impress? You might start planning an excuse for the mess, but chances are you would also be frantically cleaning as quickly as possible, trying to present the best face possible. You would not let the fact that you didn't have time to clean everything perfectly stop you from trying to at least present a decent appearance.
Suppose you went to take an exam. And in that exam you had to answer questions that you had never seen before. What would you do? You would do your best to answer, right? Presumably, if you're writing a dissertation, you managed to answer exam questions quite successfully many times over the course of years.
What if you treated your dissertation, or pieces of your dissertation, in a similar fashion? What if you wrote them in an attempt to put together a complete piece in the time you have allotted for that?
Of course, one problem with the dissertation is the distant future. When you have only one hour, or three, before the hammer comes down, it's easier to maintain focus. The dissertation is months, maybe even years away. This distant horizon is problematic--it allows one to choose to defer the effort required to write. Or perhaps it allows one to defer the fear associated with writing. And thus we have procrastination.
But I think this is something that we want to work around, and that we can change our relationship. It is a matter, I think, of looking at the writing itself as an exploration--an attempt.
Suppose one sets a task--perhaps that task is to write an abstract, perhaps it is to write an introduction to a chapter, or to write a section of a chapter--we can call that task X. One then has a choice about how to approach that task. One choice might be to say "X must be accomplished perfectly." This choice, obviously, is the perfectionist approach that is so strongly related to procrastination (see, e.g., Fiore, The Now Habit). Another choice would be to say "I will attempt to complete X in a set time; I will cover all the parts of X, even if there are some imperfections." I would suggest this choice is basically the course of action we choose in the tight moments, when feedback will be immediate and it is obviously better to do what we can in the allotted time than to do nothing.
One thing about this approach for the writer is that writing itself is a process of learning, so if we decide to take the "exam" approach, and we generate a poor draft in a short time, we still have generated something to work with, and we have learned from the process. And then we simply try again. If we expect and plan on the iteration--the revision of our work--then it becomes much more sensible and reasonable to choose to try to put something down--even if that something is going to be problematic.
When we enter our house and it's a mess, and a visitor is coming, we know what to do to try to make the house look right. We know that we're striving for appearances. We may stuff things into closets where they don't belong, but we're trying to satisfy an image.
When we sit down to an exam that asks an essay question, we know that we want to try to create and organized and coherent answer to the question--who hasn't had a professor suggest outlining exam essays during the exam? We may not have time to pull together a really coherent essay--perhaps we have a new insight in the process of writing--but we do our best to generate a coherent whole. We do our best in the time allotted to create a piece that works.
What if we were to sit down and allot ourselves a set time--say 90 minutes--to accomplish a difficult task--like writing an abstract or writing a two-page section of a chapter, or writing an outline for a chapter or a chapter section? Could we then generate a draft of a coherent whole in that time? I believe that if you have passed essay exams in a college career, then you can generate an appropriate draft. That draft might not be very good, but it would be complete.
The problem with this pair of analogies is that both have a strong streak of negative reinforcement: in both of the analogies, there is near-immediate feedback, and potential for unwanted negative feedback. With the dissertation, there is no fear of immediate feedback from anyone (except, possibly, yourself). On the one hand, I think it a long-term mistake to set up patterns based on negative reinforcement, because such situations can create resentment and fear. On the other hand I like to use these analogies, because they point out the matter of choice: one can choose to act to create an imperfect solution. And that ability exists even when the immediate negative feedback does not loom.
This perspective--this recognition of our ability to choose to write an imperfect draft, and our ability to use that draft to learn and refine our work--seems to me to be crucial for those of us who fear that we cannot write well enough, or that we have not entirely worked out some aspects, or even some of the larger issues. If there is something that we don't think we can articulate, then that is precisely the time to choose to write something imperfect. By writing the imperfect draft, we can look back at our work and learn from it--we can start to get a better idea of what it is that we have not figured out.
The short version of this: choose to write, even if the result is imperfect. The benefits of having written will justify the creation of a draft that needs to be revised.