Don't get it right -- get it written.
My friend George Ernsberger had that motto up above his typewriter (yes, writers once used those medieval torture devices), and is one of the best pieces of advice a writer can have.
How do you finish that novel? You do it by finishing it. Write it all the way through.
If you're hung up in the middle of it, if you're not satisfied with Chapter 9 and you keep revising it over and over, you're not doing that because Chapter 9 isn't good enough. You're doing it because you're afraid to finish. There's a barrier that you can't cross.
You're afraid to finish because you're afraid that when you do, it won't be good enough.
Well, cheer up. It probably won't be. Most first novels aren't. That "first novel" which just got the 6-figure advance, that made the best seller list, that Joyce Carol Oates wrote the cover blurb for saying that she couldn't put it down, that the critics compared to a young FItzgerald...that was probably the third or fourth novel that our newly successful first novelist actually wrote.
So your obligation right now is not to posterity, and it's not to the best-seller list, and it's not even to your agent-to-be. It's to yourself. And your obligation to yourself is to finish that novel.
Maybe it will be great, with a little revision. Or with a lot of revision. Or maybe it'll be fodder for the incinerator. But the point is, it will be finished. You will have written that last page, and typed "THE END" at the bottom of it.
And then you will no longer be someone who's working on that novel. You will be someone who's written a novel, and you'll be amazed at how differently that makes you view yourself.