I've been working on the project I'm focused on right now for about a year and a half (which includes time taken out for my job(s), a relationship, walking my dog, sleeping, all that good stuff). It's an old idea that was born when I was in high school (someday I'll tell you that story), but never really came to much until I started working on this draft. Anyway, I've always loved all the characters, and the setting, and I've always thought that there should be a sequel to the story, although I've always been hazy on what, exactly, that sequel would look like. I think I've a got a little case of that Author Crush on her characters, so I didn't want this to be the end. So, from time to time, I've had ideas for scenes that I liked, but they never really hung together because I never had a plot to hang them on.
Then, this weekend, while I was proctoring an LSAT practice test for my students, it hit me. I was working out a problem relating to my villian's motivation and his role in the larger scheme of things when, suddenly, BAM! like a bolt of lightning, I knew what the sequel was going to be. I even know the title (although, that, of course, is subject to change, assuming that the first book ever gets published).
The cool thing is that the sequel, while a great idea and plot, is also totally not essential. The first book can stand on its own. That has always been very important to me - I hate books that require sequels to make sense. So this first book, which was concieved of on its own, still works great, and the sequel will also work great (depending on execution, duh). Just having that idea and my other new project on the back burner really helps me keep my energy up for the revisions on this book.