The number of days that you go without actually writing something on your project equals the number of hours (one hour for each skipped day) that it will take you to actually write something once you sit down to do it. Five days = five hours at the desk before my brain really engages.
Rewriting and even retyping what you have written is a good way to prime the pump for writing. You retype your own words, and the ideas start to change them as you write.
You might be in the midst of a writing project if every time someone gets introduced on Colbert, The Daily Show, or Fresh Air as "the author of a new book on X," you see it as a dog whistle-level reproach ("why is his book finished and mine not?") and inspiration ("someday that will be me, except without the fame").