I get excited about something, then I lose any and all interest. Two weeks ago I could write 1,000 words a day on one project this week it is more like 200 words a day on a couple different projects. *sigh*
Sorry to say this because I know you won't to hear it.... but self-discipline really helps.
Pick the one you love most. Yes, there really is one. If you don't believe that, pick one at random. Five minutes later, you'll have come up with a reason to change to your real favourite.
Next, commit yourself to getting to the end of that favourite. You can worry about all the others after you finish a draft.