That's OK. You've got to go through the rejection process. Get out there and start collecting NOs as fast as you possibly can! Collect them. Own them. Embrace them. Let's say you send out your book to a hundred people and only ONE is a good fit for you. Ergo, you need to get a few dozen NOs before you get a YES. Heck, you might even get 99 NOs before your YES.
What really sucks is no answer at all. So, I'm thankful for the NO. Now I'm not sitting here wondering if my query letter got caught in their spam box.