I know all about getting to the end of enjoyment of a game.. Haha! The way I usually break myself away from a game is figuring out how to get into God mode and just ruining everything for myself.
I really don't know why, but I recently started playing Anarchy Online again. I used to be insanely addicted to it from between 2003 to 2006 or so. I haven't ever found another game that draws me in so much. Even though it's super old at this point.