We are the only species that emotionally tear from the experience of sadness as well as joy and gratitude.
Some philosophers have hypothesized that the feelings of pleasure and pain are part of one and same continuum. Pleasure has often been compared to a form of alleviation of pain. When pleasure is perceived, one associates it with reward. When pain is perceived, one associates it with punishment.
Roman poets, ancient tribal drawings and even the Kama Sutra all refer to safe practices of what has come to be known as BDSM. This acronym, which refers to Bondage, Discipline, Sadism and Masochism, reflects the ancient sexual rituals of dominance and submission that have qualified sex throughout history.
We make a difference between good pain and bad pain. Bad pain indicates that something is not right, something we have to pay instant attention to and then there is good pain which is enjoyable.
Loving someone emotionally creates the same pleasure / pain experience that lives in the body while making Love to them.
The moments of deep connection and intimacy, vulnerability and nakedness are matched by their opposite experience: feeling deeply hurt by your lover, by what was said, or, just as often, what went unsaid.