A lot of people are motivated by deadlines. I often have people tell me that they work well under the pressure of a deadline. The thing is that deadlines really only work for short time periods. One cannot really sustain the deadline type of pressure for the length of time it takes to write a dissertation or a book. And realistically, one would not want to develop a work habit that requires high-stress work all the time in order to be productive. If the dissertation is preparation for an academic career, wouldn't it make sense to try to develop a work practice that will support you through an entire career?
But there are some good things about deadlines. And I'd like to look at those aspects of working to a deadline to suggest that they can be principles that you use even when you're not faced with the pressure of a deadline.
There are two very important aspects to working to deadline that many writers don't see: 1. Deadlines force the writer to abandon perfectionism and 2. the writer must prioritize efforts so as to create a work that is balanced and complete--complete in the sense that all the parts are included (i.e., no notes that say "Add section on XYZ"), and balanced in the sense that all the parts are equally finished. These two factors really work together.
The value of completing the whole piece is great: by completing the whole work, by writing drafts of all the chapters, the writer can see how all the pieces work together, thereby giving further definition to what each piece must look like alone. I feel like I run into a lot of people whose professors tell them to do the opposite--to work on one piece at a time. Of course you need to write one chapter at a time, but having done an initial draft of one chapter, do you then go back and revise that draft, or do you draft the next chapter? I recommend drafting the next chapter. When working towards a deadline, one always includes all the necessary sections.
When working towards a deadline, in order to get all pieces of work equally done, it is necessary to prioritize. Generally one wants to finish with the piece being worked on, and move on to the next piece is basic accordance with a schedule. When taking an exam, one is well-advised to budget time according to the value of the questions; similarly when writing several seminar semester papers in the closing weeks of a term, one is wise to budget the time amongst the different papers to ensure that all of them are addressed. This prioritization allows us to put aside perfectionist tendencies. If we've ever successfully worked to meet a deadline, then we've managed our time to accomplish all the allotted tasks, and almost certainly put our perfectionism aside to work. It's a choice that we can make to help us make progress: we can say "the work needs to be brought to the same level of completion as the other pieces I've already worked on."