"The definition of a competitor is the guy who keeps coming back. It's the difference between the grass and the oak tree. Cut the oak tree, and it dies. Cut the grass, and it grows back." - Sandy Koufax, from SANDY KOUFAX: A LEFTY'S LEGACY by Jane Leavy.
Rejections are a strong element of publishing, whether you're an author, agent, or editor. It's good to be grass in this business.