It can calm (at least myself) during any time I am stressed. Though I suggest refraining from doing so around others. For me Stress + some form of "self harm"/my case I don't feel it = numbness/good thing so I can start thinking clearly again. If someone does engage in some form of self harm, I'd advice trying to confine it to areas of the body where marks cannot typically be seen & avoid hitting/banging the head. Worst I've gotten from hurting myself (usually I jump around & end up banging my walls (which I don't feel at all, don't even know I hit something 'til I hear the bang from my body hitting something). Though now I'm trying to use an exercise ball & stuff to curb it so I don't damage my dorm. If someone a scratcher or skin pincher, etc. (I am on rare occasions/again half the time don't even notice myself doing it 'til I find scratch marks &/or mild bruises) they should keep their nails short (avoid fake nails).
p.s. mild bruises = small bruises on arms or legs (maybe 1 on the back) but most under the size of a quarter (less than to 3/4 in. or 1.5 cm on average/no bigger than 2 cm in diameter) and they fade off in a week or less.
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Balance is needed within the universe, can be demonstrated in most/all concepts/things. Black/White, Good/Evil, etc.
All dependent upon your own perspective in your own form of existence, so trust your own gut and live the way YOU want/need to.