Well, the whirlwind that was November is over. The deadline has come and gone, and you've had a day to lay comatose with ice on your wrists. You've managed to crawl out of bed long enough to check your blogs, so I have a very important question for you: how did it go?
Here's the thing about NaNoWriMo. It gives you a goal and a deadline. But the only reason it does that is to get you at your desk and writing. The month is not about the magic number, it's about the writing. It's about proving to yourself and your characters and your family that you can make time to tell stories. And you showed that.
The most important thing is that you wrote. Whether you ended with 50,000+ words or 25,000 words or even 2,000 words, you ended the month with more words than you started with. As long as you wrote something, you won!
You may want to keep working on your NaNo novel, or you may not. If you do, take some time to let it sit first. Give yourself some time to recover from the craziness of the month. And, when you're ready, get the manuscript out again, read through it, and start tweaking.
If it stays in a folder on your computer forever, that's fine, too. Sometimes a NaNo novel is just something you wrote one month. (You can always use it for parts!) It still showed you that you can do it.
Just because it's December doesn't mean you have to stop writing. Keep the motivation and excitement from NaNo through the rest of the year. Use it to fuel other projects, edit your WIP, start something new.
Just keep writing.
And congratulations on all you accomplished in November!