It hits like lightning across the forebrain. The Brilliant Idea that will be the Next New Book. And every thought is consumed with the "Oh, wow!"ness of this new idea. It's fresh and exciting, especially if it hits in the hard-middle-slog of a novel. Then, it inhabits your brain like new lover, with promises of how everything is going to be easy and light and problem free and THIS is the project you should be working on.
And the initial worldbuilding snaps together, characters are as clear as day. You open up a document and just start writing, because isn't that's how it's supposed to be? Isn't that how real writers write, right? They just pound it out and go where the story takes them and they do it brilliantly on their first draft and that's what you're going to do this time because it's brilliant and you're brilliant and this is the best novel ever written by anyone ever and--
Somewhere between five and fifteen thousand words, the fiery passion part is burnt out, and then you're poking at those dying embers and realizing, "I don't actually have a plot here, do I?"
So you put it do the side, mourning its failure for a bit. Get back to work on the things that need work, where the work is paying off, slowly and surely.
But, of course, the siren call is there, summoning you back with the promise that this time it's going to work. This time it's going to be brilliant.
I've gone through this particular cycle with USS Banshee several times now. I do have a good sense what "went wrong" on my first few attempts: namely, that lack of plot. But with later ones, it was almost as if I didn't want to actually get to the plot. Put simply, I kept wanting to just write a "hang out" book. I was having fun with the various sets of characters in different sections of the ship, just playing with the personalities, showing off shiny toys, that I could never manage to get to the point where they went anywhere for something to actually happen. One failed draft reached 40,000 words of NOTHING.
That's the most prominent false-start in my stable. I keep coming up with new takes on it, one of which I'm currently quite excited about. Still hashing it out, but I think this one might work. But I've thought that before. Not to mention, there's all the "terminal cases" I have in my writing folders. But USS Banshee is, frankly, the one I can never give up on.