I volunteer weekly in a school for youngsters with special needs: they're some of the most genuine, amazing characters I've ever met. Truth be told, I find it so much easier being with SEN youngsters and adults than with non-SEN people. Anyway, today one of the youngsters was agitated and jerkily hit himself a few times in the face to calm down. One of the staff members wondered aloud why he did that, and how curious it was that it helped.
Sometimes when I'm agitated, I'm really tempted to jerk and sometimes end up hitting myself. It feels like there's too much energy bubbling up inside, and this is a quick release. If I'm on my own, sometimes I allow myself to do this (I never hit hard, and it somehow does help calm me down) - I lightly slapped my cheeks with the backs of my hands just now, that helped bring me back to reality. I'm most likely agitated due to revision stress, and having a large dinner - the extra energy and the stress certainly don't make me feel calm!
Just to clarify: this is completely different to self-harming. I don't do this to punish myself, or to feel pain, and I don't have much conscious control over where my hands do end up (sometimes this has resulted in me slapping the back of my hands against a wardrobe, or chairs, or door handles if they're in the wrong place at the wrong time). It's just an energy release. I understand why some of the youngsters at the school do this.