I just got a rejection email from an agent, and at first, I had this weird reaction. I didn't feel rejected. I felt more like I had gotten a bunch of suggestions for revisions that seemed hard and time-consuming and impossible to complete.
Now, reflecting on that feeling and rereading the email, I've realized something important. This is familiar territory. Even though it was technically a rejection, this agent gave me some suggestions, which means my reaction is up to me. I can view her rejection as a list of revisions instead. That means, I can do what I always do with revisions: Feel overwhelmed. Wait a few days to work on them. Then, start addressing each comment one at a time.
Even now, instead of feeling rejected or even overwhelmed, I'm getting excited. In a few days, these revisions won't seem so difficult to address. I'm pretty sure this is what it takes to succeed in this business: Just keep working!