Pain Can Calm.

Little bits of pain can provide relief and peace in a way that is highly addictive.   There are explanations.  Of course, if you don't expect pain and have it inflicted on you, it will not prove calming.  But if self-inflicted, and controlled, once gotten used to, it can provide some comfort, if you will.  Hence cutting, self-mutilation, etc.  Once you gain a 'tolerance' you can go too far.