So far, I've been resisting the urge and haven't cast on anything new since the new year. To satisfy my lack of ability to focus on any one project, I've been jumping around putting a little bit of attention into one or two of my WIPs each day. On the one hand, this satisfies my desire to constantly be working on something different, on the other hand, it also ensures that I continue to feel like "nothing will ever get done" that tends to bring on startitis in the first place.
Today, the project du jure was a fingreless mitt I've been working on, which will (hopefully) be part of a pair someday.
So far these have done a pretty good job of keeping me interested--they have that colorwork "just one more row" magic--but I suspect that as soon as it comes time to make the second one, working the pattern a second time will seem less charming. I will resist casting one 15 new things. I will!