Sometimes I have inspiration for a story. In random pieces of spare time I daydream more and more details until I am satisfied with the concept and then I don't take it any farther. In my head, the story is finished and I am satisfied. If I have the urge to write it down and attempt to share it with others, the thing that stops me is that I do not know if anybody would actually read it. I like it, but that doesn't mean others would.
Often, the stories I imagine do not have a "message" or "explore new possibilities" or attempt to "answer important questions" like the meaning of life - they are often fantasy, just exploring a character's path through life.
Since writing is not my profession, I do not need to write, and I find myself thinking that the world doesn't need another amateur story lying around.
How should I decide whether a story is actually worth writing out and sharing with others?