@Ragdoll Circus I concur. :)
I do lots of body focused repetitive stuff, like twisting my hair, picking at my lips, bounding my foot, etc.
If I can do these things, then I'm not being attacked. I do think that it is a way to tell the body "hey, we're safe. settle down in there." And some parts need that safety demonstrated in these tangible ways.
My sister used to bite her nails very low. Same thing. Now she cuts, unfortunately, and using eating disorders.
Behaviors that seem maladaptive but help to remind of safety. Same thing.
Supposedly, it can be good to carry small, smooth stones, a stress ball, or a beanie baby toy around to mess with in the pocket so people cannot see. Some use prayer beads to fuss with.
I once made homemade lavender beads to wear as a bracelet. Smelling it and or toying with it seemed to help ground me.