Original Ideas are Fragile Things

I generally prefer novels to short story collections, but I would read a shopping list if Gaiman penned it.
I received Neil Gaiman’s collection of short stories Fragile Things for Christmas, and I’ve been devouring it rapidly. My favorite so far has been a gem called “Other People.”
The story details a man’s punishment in Hell, where he is physically tortured by a demon. He’s then forced to recount his life aloud again and again, admitting to every bad thing he’s ever done, and then he’s forced to learn the repercussions of his selfishness on other people.
In the end, the torture has left him looking like the demon, a soulless husk, and a new wayward human enters the chamber. The cycle begins anew.
In the forward, Gaiman recounts the doubt he felt upon completion of the story. It felt too circular, too neat to be original. It nagged at the back of his mind. He was sure it must have been a story he’d heard years before and then forgotten. After reading “Other People” to a number of friends, however, no one could name a derivative work.
I think this is a problem all writers face. Whenever I get an idea for a story, if I don’t get it written within a day or two, I usually talk myself out of it. I tell myself it’s too much like this other story or it’s taking too much from this movie.
Art doesn’t exist in a vacuum – everybody draws from their role models and inspirations. What separates us from them, though? How do we differentiate our work, and how do we mark that difference between being inspired by an artist and stealing from them?
I wrote this briefly and in a quick stream-of-thought during a fit of “not wanting to do my planning that I’ve put off for too long”. If I had more time, it’d be shorter. Sorry.
Okay, so I’ve been meaning to respond to this for awhile, and I’ve just totally neglected it. I’ve read the same foreword and I think I share a similar appreciation for Neil Gaiman, and it’s been awhile since I’ve read it. Did he present it as a ‘problem’, this feeling that a writer is subconsciously (or consciously) borrowing from another work? I ask because I’ve never regarded it as a problem, but more as a reality (which I think you do, too, as evidenced by your last paragraph). We are inherently influenced by the stories we hear or read – news, books, short stories, novels, you name it – and I don’t think it’s a real expectation for any writer to be totally original.
Sure, there are always going to be more unique story concepts or presentations, but I can assure you that this concept is still influenced by something else.
Now, on to your question at the end of it. Many things will always differentiate you from your models, particularly if you are a “sit-down-and-write writer.” Your stories will still have your own style, your own prose, your own dialogical tendencies, to differentiate you. Theoretically, you could read a book and copy the style in your own, but I think that’d be even more tiresome and difficult than actually doing the writing yourself. Even then, it’s not plagiarism; it’s kind of a relearning. Though immoral (to yourself, mostly, I’d suggest), I doubt it’s illegal to mimic a writer’s structure.
The below is loosely related, not directly
Plagiarism is DIRECT copying, DIRECT stealing of ideas and even words.
Example of plagiarism accusation –> someone sued J.K. Rowling because she was writing a story about kids who go to a magic school and also take a special train. She lost, as I understand it, because it was implausible for Rowling to be familiar with her work. (Rowling has been sued by more than a few people).
Example of plagiarism accusation with an end–> A romance novel a la Harlequin had a scene with ferrets (or some such rodents) copulating, taken directly from a scientific text. The original writer sued to have it removed and won.