The answer to that question about masochism is that masochism is probably one of the strongest and most universal sources of inspiration in the animal kingdom (venus in furs style, baby)(think of aggression (increased cell-death) as a sort of masochism). This is the reason cutters cut--opiate release from induced mass cell death. Masochism, stressing the system, helps; and blocking that induced pain signal becomes a priority of some unknown system in order to maintain the illusion of homeostasis for continued high-level functioning (not dwelling on pain). We do have a very powerful recharge system, which in the presence of pain accumulated throughout the day, seeks to use as little energy as possible, shut off sensors, and go to sleep. It's our sleep system, and our seeking-safe-shelter-to-do-it system. This system has many other important functions, we can begin to think about. To better frame this confusing problem, another parable:

Let's say your girlfriend of two years dumps you and fucks some ugly oboe playing retard from her work (and she gets thrown out in the morning). you have no friends because all you really care about is safe sex, drugs, and odd electronic music that's pretty difficult to listen to, but the only successful therapy you can find. so, you decide to curl up on the carpet and die. how long is that going to last? 6 hours? 8? sooner or later, the pains in your stomach will get so bad, that you will inevitably walk over sulkily to the refrigerator and find all your favorite comfort foods. point- it is really hard to want to die.