Oh. Even the word sounds harsh and final. No matter how you school yourself against it, the feeling you get when your novel is returned is not nice. The tendency here is to see a rejection as not only of your novel but of yourself- your idea, your creativity, intelligence, talent and above all your writing.
My advice here is to indulge in this welter of self-pity for a prescribed time limit. No more than 1 - 2 days, then you get annoyed with yourself and give yourself a good talking to.
Almost all writers get rejections - they are part of the process of getting published.
It isn't personal - no-one is just being nice to you (in publishing "being nice) is rare. It is often the case that your book just doesn't fit their list at that time.
You will get there in the end.
Always have something else in the pipeline. This may be another agent/publisher or a different project. You know what they say about all your eggs in one basket.
Have a writing buddy or group that will support at this point.