It really doesn't work, but I've been taking showers every day, frequently cutting my nails - all to stop a feeling of grossness that seems to trigger it - and when I go to bed I lie on my hands to keep them still. I've also had some success with homebrew habit-reversal training, although the several times I stuck to it, life kept coming back to kick me down... Sometimes when I'm jittery I hit my hands together and that seems to relieve the urge, for whatever reason. Maybe it's the same pain hormones.