Writers are weird when it comes to the end of things.
Writing a book is an investment in time, resources, talent and imagination. It is perfectly natural to feel anxious when you come to the end of this process. It is an expenditure! There are famous writers that take time to decompress after finishing crafting the world with these ink and paper people. Again, a part of yourself goes into the making of these worlds and people! Why would you not want to rest?
Yet, you must. Your mind and body will insist on it. Even if you have to take breaks between drafts, this will prepare you to say everything that you need to say–so you can get it all out! One of the tricks with writing is to be brave enough so say everything you need to say, even if you need to take breaths in-between.
Rest. Write. Repeat.