The war is over. What now? You've got 50,000 words, maybe more, of a story that may or may not be worthwhile. I know the feeling of getting to December only to look back over those words and think, "Uuuuuugh. I wrote that?" or, if your story isn't complete: "I wrote that much, and I still have this much plot left? You're kidding, right?" Come NaNo's end in both 2009 and 2010, I was terribly burned out; both times, however, I tried to keep going. Bad idea. When the wordcount closed and December rolled around, I was tired and all my inspiration was toasted, while in the back of my mind lurked the knowledge that those 50,000 words would have to be seriously revised. December and January produced a whole lot of groans and whines, and maybe some tears and sweat (no blood), but not many words.
Probably the best thing to do when you reach the end is to take a break, at least from that particular story. Give yourself time to recharge. You might go back and look at the story you were working on before NaNo; if it is completed you can work on editing it, or if it isn't you can return to writing it. Time away might bring to light new inspiration or reveal things you want to tweak. In December 2010 I worked on editing Wordcrafter, getting my mind off the big problem that was The White Sail's Shaking, and didn't spend a whole lot of brain power on straight "writing". This isn't laziness. Editing and marketing are just as important as writing itself is; manuscripts once completed shouldn't just be discarded. So don't feel bad if you need to take a break and spend time on another story.
When I had gone through the initial edit of Wordcrafter, I returned with more vigor to the writing of The White Sail's Shaking. It's now too long ago (a whole year - dear me!) for me to recall exactly what my sensations were, but they were not pleasant. The rubbish that was the first 50,000 words tortured me until at last I gave in and started editing much of what I had written in November. Filling in holes, straightening out characters, and fixing botched details helped get me back in the feel of the novel, and when I had finished with the first few chapters, I was ready to return to actually writing again.
But what if you wrote your story just for fun and don't intend for it to go anywhere? I know some people approach NaNo as a time to just let the rules fly out the window and allow themselves to write whatever occurs to them, not worrying about whether or not the result is any good. I tried this in 2008 and it went splat at about 17,000 words, but hey, it works for some writers. Even if this is your perspective on NaNoWriMo, you can still glean things from those 50,000 words. Let the story sit for a while, then return to it, read over it, and make your assessment. If you find that it's actually not that bad, you might want to spin it out and make a proper novel out of it after all. If you decide that the plot is just as nonsensical as you thought at the end of November, then perhaps you can focus on picking out those bits of your writing that you still like - a description or a turn of phrase, a scrap of dialogue, a character. You may be surprised how many diamonds you find.
what was your wordcount this year? do you hope to make something of the story?