No one likes having their writing rejected. It doesn't matter how good an author is, they will have someone say, "No thanks, I don't want this." Rejection can come from a piece of paper in the mail, a general e-mail, or a one star review on Amazon. The feeling that no one wants your work can be devastating, and turning your attitude around after you get a rejection letter is extremely difficult.
This past week, I got a tan piece of paper in the mail, describing some disinterest in a writing project of mine. It hurt. I won't deny the pain rejection causes, but I had made up my mind before I even submitted that I would be content with whatever God chose to do with my work.
Before you submit, ask God to keep your focus on what He can do with your writing, rather than what an individual's choice can do with your writing. Ultimately, what He will do is so much better anyway, but it's much harder to remind yourself of this after the rejection. Remind yourself beforehand.
Let God wow you, not a publisher, editor, or agent.
Disappointment happens but you can know that "surely there is a future, and your hope will not be cut off," (Proverbs 23:18)