The students in Lamott's classes always ask how you know when you're done. Lamott says she doesn't quite know how to answer that question. Apparently, you just know.
There will always be a bit more you could do, but eventually you will realize that you are done, and it's time to move on to the next thing.
Lamott says that people in recovery from addiction say that getting all the addictions under control is like putting an octopus to bed. According to Lamott, that's what finishing your final draft is like, too. You get one problem under control and another pops out, like an octopus tentacle coming up from under the covers.
But basically, there will come a point when you've done a lot of fixing and you're completely exhausted and even though the manuscript isn't perfect, it's the best you can do for now, and then you're done.