I'm sure anyone who's written a novel has been there. It's taken me 25 years or so to realize that there was something I was supposed to be doing, and I wasn't doing it. Now that I've found the thing that makes me feel complete, all I hear is the word no. No one does this quickly. No I'm not sold on your novel. The no's pile up, and sometimes it's overwhelming- particularly because you want it so bad. If writing were a whim it wouldn't matter. But it's not a whim. It's a dream. And sometimes that dream feels as if it's made of very delicate glass.
In my experience, there is always this roller-coaster. I finish a novel that I think is great, send out queries in a flurry of excitement. Sit back while rejections roll in. But by the time I've given up on that one I have already written something new. Something better. I'm excited again. Repeat.
I got a rejection today from what I had hoped would be the perfect fit. That burned worse than the slowly healing road-rash taking up a quarter of my leg... but that's another story. Anyway I let myself wallow a bit. Then just now I opened up the short snippet I've written on my next novel, fully expecting to find unintelligible crap that no one would ever want to lay eyes on. Instead I found something valuable. I read what I had written (first time since I banged it out in a rush between family trips) and was pleasantly surprised. It wasn't crap. In fact, I think it was a heck of a lot better than crap. I kind of fell in love.
I guess the moral of the story is this: next time you doubt yourself, go back and read something you've written. Not your current project, but something that's old enough to feel new to you. Read it with the eyes of a reader, not a writer. Did you just get sucked into what you had written? See... you can do it. Get up. Brush yourself off. Put some ointment on the road rash.... uh I mean, put your fingers on the keyboard. Let it take you somewhere.