Rejection, the writer's least-favourite word. It means a letter in the post, or an email, saying the agent or publisher doesn't consider your story or novel worthy of publication. Reading between the lines, that correspondence is telling you that you're writing isn't good, your characters are weak, your plot is paper thin; it asks why you've even bothered.
That's not true, of course. It can feel that way; it certainly did when I sent my first short story to a magazine over twenty years ago. Looking at that letter now, it's kindly written and offers solutions to what the reader thought were the problems. Back then, it made me give up and - two decades on - that story's still in the same plastic folder gathering dust. A couple of years after sending it away that first time, my mum asked why I hadn't done what the reader had suggested. I had no answer, no logical one at least, and all I could do was shrug my shoulders.
My latest short story - an urban fantasy set in 1960's Paris - has been rejected twice. Rather than give up on it, I've actually been encouraged by the comments. The first suggested it could be expanded into novella length or beyond, while the second felt sure that, although the story was not for them, I shouldn't have trouble finding a home for it in the future. Kindly written, just like that one twenty years ago, only now I'm mature enough to see that.
I've written before saying that courage is about facing fears rather than not having them in the first place, and fear of rejection can stop a person doing many things. We've got to take chances in life, have that courage to do what we believe, have the strength to carry on no matter what people think. Don't give up; keep going, and eventually there will be success.