I actually didn't speak of psychology of pain though. That is a whole different subject entirely and highly personal to each of us. From a biological standpoint, pain is biochemical and physiological. What each of us does with what we feel...well, that's where psychology comes into play.
Actually, the majority of our perception of pain is psychological. Pain in and of itself is a stimulus which can cause some enduring sensation and reflexive actions, but most of what we consider to be the feeling of pain is psychological suffering. It is actually hard wired in the brain, the pain centers sit right by the part of the brain that is responsible for most emotions, the amygdala and the hippocampus.
Everyone feels pain, in all instances however not everyone feels suffering. There are endless ways that we can impact our emotional response to pain. There are endless responses we can have. The brain's preferred pathway of pain stimulus received by the thalamus triggering emotional perception of pain and suffering is not the only one. For instance if we ascribe love and arousal as a response to the pain response the majority of what we know of as pain is not being experienced. Human beings mostly rely on the end of the process in regards to the interpretation of stimuli. Our emotional response to things is largely how we sort out memory in the brain, along with how we remember things. We have countless ways to perceive stimuli in that regard, pain being only one of them.
Peer reviewed article on the psychology of pain: http://williams.medicine.wisc.edu/painpsychology.pdf
This is exactly why psychology is getting so involved in the treatment of chronic pain.
However, when it's pain I enjoy I no longer view it as full on masochism, same goes with my partner and my practice of sadism. Fully engaged masochism for me is when I am experiencing psychological suffering for the benefit of another, which is also the sadomasochistic aspect in our relationship in regards to power exchange.
Our intimacy tends to be so edgy because so many things that used to provoke a response of suffering, no longer do. Also, the deeper down the rabbit hole we go the more that pain AND suffering is something we both seek out. We tend towards finding twisted new psychological ways to bring out fear, humiliation, and a healthy sort of shame. Along with constantly bringing new physical techniques/tools into the relationship.
New pain sensations, and a fight/flight and/or negative emotional state are great for evoking suffering.
Pain AND suffering are DEEPLY intimate and erotic for me. Pain gets me wet, suffering binds at the soul. It is pure vulnerability and connection for me, and the flow of suffering feeding another is my favorite means of experiencing power exchange, from either end of the spectrum.
Oh my darling, give me reason
give me something to believe in
You need a spankin' baby!