NaNoWriMo is a joke. The year I tried to write 50,000 words in month, I ended up with a gluttonous stack of words, like vomit over paper, like a free-writing exercise in some sort of creative writing class in hell, the whip-wielding demon behind me roaring, "More! More!"
If you want to write a novel--a rational, fleshed-out, character-driven and reader-worthy piece of fiction--I'd say set a reasonable daily goal and stick with it. There's no way around it. Write a little every day and eventually you might actually have a novel. Then, of course, you'll probably have to write another one, but if you enjoyed writing the first one, that shouldn't be so bad. Just write, but don't worry about speed; worry about quality, about character, about story, about atmosphere, however you come by it, in your own way, in your own time. Have fun with it. Start your novel this month, and write until it's finished, but be careful, and don't rush it; there's no need for that nonsense.
Of course, if you're lucky enough to be a full-time writer and don't have some stupid day job looming over you, consuming your time like the aforementioned demon's mentally challenged cousin Angus eats brimstone, there's a good chance you write a solid 50k each month anyway!