'The End' might not be, after all. Stories have a habit of refusing to go away, insisting that there's still life smouldering between the lines, no matter how many times it's been discarded or rejected.
For years, I've advocated, 'never throw away your failed tales'. I've resurrected several and they've been sold subsequently. Certain stories - or their theme or idea - are just not ready; whether that's the treatment, the characters, or the lack of writing experience; for some reason the story needs time to gestate.
A writer friend, Ray Foster, can certainly endorse this viewpoint. A story that evolved in 2000, changed and morphed in the intervening time until finally being accepted for an anthology this year, the third in an ongoing annual series, Spectacular Tales. Let him tell you about it here.
Of the many instances where I too have found that time was necessary to let the story grow, perhaps the first adventure of Tana Standish is apt. It began as a short story in the early 1970s, transformed into a 50,000-word novel in 1975, and was rejected by Robert Hale due to its paranormal elements (a psychic spy), though their rejection did say 'it's better than many books that are published'. Years later, I returned to the manuscript, piled up a great deal more research, and it was finally published in 2007 as The Prague Manuscript (84,000 words). Then the publisher ceased publishing and the manuscript languished until I revised it yet again and it was published by Crooked Cat in 2014 as The Prague Papers (75,000 words). Since then, another novel in the series has resulted, The Tehran Text (85,000 words) and a work-in-progress is 60,000-words and counting, The Khyber Chronicle.
So, take heed of Ray's closing comments, and never give up.