Abstract
From evolutionary point of view, pain and pleasure are some of the most important processes for survival. The pain serves as indicator that the causing activity or stimulus should be avoided for its potential to cause harm.
Conversely, pleasure is pleasing and shall guide the organism or individual towards repetition and benefit. There are various stimuli that may bring pleasure such as food that is also beneficial for survival.
Thus the two processes are not always distinct and countering each other. There are moments when one experience can cause or potentiate the other.
Concretely, human sexuality is a field where the two can coexist and share the paths. Pain may bring or potentiate gratification and pleasure.
This may be the final reason why people intentionally search for these intensive experiences.