This is a solvable problem, it seems to me. Rather than being afraid of being done, I can have many (or more than one) project going at once, that way they overlap and not only can I switch back and forth from one to the next, I can also be sure that the other one waits for me when the first one is, or seems, done. I know this is a trick of the mind other writers have been relying on for a very long time, but we all seem to recreate our own version of the wheel.
It's odd, isn't it, that one procrastinates on things one actually enjoys? I can find eight different things to do that aren't what I should be doing. I have become a consummate artist at puttering and doing nothing. Procrastination also ties into the lack of discipline that has been plaguing me for years now. I have to keep pushing myself, and going back to my research to inspire my writing. I read books on the Ancient Greeks, and all of a sudden, I get ideas for my characters.
To help avoid avoidance, I leave my laptop on all the time, with my current chapter open where I can see it. This seems to remind me the writing is still there, waiting for me to work on it.