We say it all the time. I've said it, many times here on this blog: if you're going to be a writer, you need to learn how to deal with rejection. Here's why: it happens to all of us. I don't think there is a writer anywhere who has never gotten a rejection letter.
Even after you start selling things, you still get rejection letters. My Clarionmate, Ferrett, who has enough professional sales in his bibliography to be a SFWA member, blogs today about his 29-minute rejection letter. One day, both the first and last emails in my inbox were rejections. Even people with multiple books on the shelf have to deal with contract options that aren't picked up, proposals that are passed on, short stories that are "good, but not right for us." Rejection happens. To all of us. At all stages of our careers. (Okay, maybe if your career goes JK Rowling-style supernova you don't get rejection letters anymore. Maybe.)
But if you read carefully (as carefully as you read submission guidelines, thereby doing what you can to minimize your chance of rejection), you'll notice I said "deal with" not "like." Find a coping strategy that gets you through someone saying no. And then have a back up plan.
Because one day, you're going to get that one rejection letter too many. Or too quickly. Or after too long. Or when thirty-nine other things have already gone wrong that day. Or it will be for your favorite story, the one you feel might be your best work, and editor after editor says "this is beautiful, but not for us" and you just want to break down and cry, and beg, and say "How about I pay you to publish it?"
Have a back up plan, so the frustration stays in your head, and off of your blog. So that you don't actually hit "send" on that scathingly worded reply to the editor. So that you keep writing.