An author friend of mine received over 200 rejections before his story finally got published. That story later evolved into 3 series (4 books in each series) set in the same story world.

He kept all of his rejection letters, and he often tells this story. He learned many years later that a young girl decided not to commit suicide because she identified with the heroine in his books. He looked back at older drafts of the story and at his first rejection letter, and he realized that if the story had been published THEN, that particular character would not have existed.

So, sometimes rejection is good, as it can force you to write the story that was meant to be.