I DO know what you mean about stories planned in such detail that you don't really have the incentive to write them, but for me, the ones that are like that are the stories that I "write" in my head when I'm falling asleep

I totally do this! It's the best way to shut down. I love that you do it too.

I also have MBs of unfinished fic, fics which have been fermenting for years. DAWK. Lords of Mer. I am in no way saying that my way works, it's just the way that I work. The quickest way for me to derail a fic is to dwell on it too much.