Rejection and Writing

You're not getting results.
You're being rejected, or worse not even being advised of your rejection.
You feel depressed.

You are however sure that you have talent enough to write well, that you know (for lack of a more clever cliche) deep in your soul that you ARE a writer. There is nothing else you can do but write.

Rejection isn't personal. 
It's not like when you were fourteen and your best friend decided they'd do better as best friends with someone cooler.
And no one is saying that you aren't a writer, or that you can't be one. The rejection is simply for the piece you submitted. The "greener" you are at writing, the further you have to go. But you must practice and practicing means rejection.

Rejection teaches you.
Writing is an art, a craft that needs to be honed. For some it takes less time than for others. Regardless, "errors" or missteps can be seen much more easily in retrospect. Rejection can show you what went wrong, especially if an editor takes the time to express the reasons for the rejections (which happens far too little I've heard.) Regardless, any rejection, explained or not, can teach you what not to do.
And it's a starting point. Worse than rejection is the waiting for rejection. So just accept it, try to learn from it and move on especially with the knowledge that...

Everyone gets rejected.
Manuscripts that went on to make millions of dollars and garner rabid fans have been rejected. George Orwell's "Animal Farm". "Jonathan Livingston Seagull" by Richard Bach. "Chicken Soup for the Soul".  James Joyce's "Dubliners". "Zen and the Art of Motorcycle Maintenance" by Robert Pirsig. Richard Hooker's "M*A*S*H". "Carrie" by Stephen King. Madeleine L'Engle's "a Wrinkle in Time". "Gone With the Wind" by Margaret Mitchell. "Dune" by Frank Herbert.

One rejection letter is not the end.
Perhaps your piece needs massaging. Perhaps you have learned to write better in the months it took to finish the manuscript.
You can go through your novel or article with "fresh eyes", with the experiences you've had since writing it. You can use the techniques you've learned and tips you've gleaned since completion to make changes. There are forums online that allow you to connect with like-minded writers and ask them to look over a chapter or two, to give you some pointers.
You can resubmit, or submit somewhere else. Sometimes someone was having a bad day, or just slogging through the last in the pile or had other things on their mind.