Do you ever look back at your original notes for a story? When I do, I often find that my story has morphed into something completely different. So much for the preliminary synopsis and one-line summary that I wrote before I started.
The mental picture of Novel #4 that I had as I started jotting down those first, excitement-filled ideas is very different from the picture I have now, after all the cutting and layering and stopping to brainstorm "what if". Through the long process of writing and revising, the story I wanted to tell has changed.
It always surprises me when my stories always turn out to be much more serious than I originally think they will (even though I don't think other people would be surprised, since I'm a fairly serious person). Do your stories change a lot from the way you originally conceptualize them?
BTW, that other story? The one I initially dreamed up when I wrote the summary? It sounds really good. Maybe someday I'll write that one too.