Hello, All can experiance pain or pleasure on different events. Commonly pain is indicated may be related to "withdrawl" and pleasure with "coming closure" (though pain from a slap or otherwise can do both in some cases). Anyway, can you tell physiological basis of getting "pain & pleasure" and mutual relations in between these, if any? Chronic pain, habitulity, tolerance, resistance and adaption to these can also be considered here. Best wishes.