Here's another tip to help with you dissertation.
Make a pact with yourself not to edit before you write. Start each working session by writing fresh material. Write as much as you can, and then use any time left over to edit. This works to diminish perfectionism, because if you have written new material today, you are much less likely to go back and change yesterday's material. But in the absence of new writing, you may work and rework existing material and never get on to anything new.
If you are working many hours, but have no new writing to show for it, you probably need to monitor how you're spending your time. It can be too easy to lose time editing what you already wrote when you really need to be writing something new.