Seriously, when I'm frustrated, I just sit there slamming my fist against my thigh as hard as I can. Also when I'm anxious or excited. So I have a bruise that's like deepdeepdeep and covers like half my mid-thigh......
*nods* And do pretty much everything better. It just helps. Or, if somebody stops me, then I stab myself in the leg with my pen. Or kick myself in the shin. Slight pain = mucho concentration.