Did you ever have one of those exes (this applies to ex-boyfriends in particular; it could apply to ex-girlfriends, too--but I don't have any experience with that) that have break-up radar? Like, they're not really good for you but they're oh so hard to get over. And when you finally start to get over them and move on with your life--BLAM--they come back full force and suck you back in.
Writing can be like that, too. Just as a hypothetical example (ahem), say this weekend I came up with a brand new idea. And this idea was so shiny and sparkly, it made me question whether I should keep moving forward with any current project. And then, in the eleventh hour, my current project pulled ahead by a nose.
That's all I'm going to say on that topic, except that I'm a bundle of nerves today and every time I check my email (about every hour or so), I want to throw up. In a potentially good way.