I hate being rejected. Do you remember the last kid chosen for teams in elementary school? That was always me. Not only was I rejected, but it was in such a public way. So, what did I do? In adulthood, I selected several creative, highly competitive fields of endeavor. What can I say, I'm kind of nuts.
In writing ,painting, and now photography, I deal with rejection every day. It hurts my feelings, and after the hurt comes a flash of anger, but after the fury comes a rush of determination--not "to do better" because that's a matter of opinion (A Wrinkle in Time, a classic, award-winning middle grade novel, was rejected 22 times before being published), but rather to create another product for the rejecting agency and/or submit the rejected item elsewhere, perhaps in a different form. For example, I submit my landscapes and digital art to print on demand sites. I set up my own calendars, cards, and other products. (If you plan to do this, check your contract. I am not exclusive.)
At conferences and expos I have met many aspiring artists, photographers, and writers who will never make it. How can I say this? Many of these people are more talented, better funded, and more academically trained than I, BUT--they cannot handle rejection. They think they are more "sensitive" than working professionals.
Bull CaCa!! Everyone is sensitive. The difference between creative workers who make it and those who don't is simple. The ones who make it want it enough to face the pain and walk through it. The ones who don't, don't.