As someone with this disorder, I can assure you that this person really does not realize he is doing it (think of friends you’ve had who might bite their nails or someone who shakes their leg). Stress, no matter how minor, can be a trigger unless there is another distraction to keep my hands busy, such as playing a game on my phone. My husband used to call me out with a “stop!” but that was so embarrassing that it generally made things worse. Now he holds my hand for a few seconds while trying to distract me, which is so much more successful.