Endorphins

Endorphins are neurotransmitters (chemicals which are directly involved in the brain's electrochemical workings). They are also natural painkillers. High endorphin levels cause a feeling of euphoria. Of course, SM is not the only way to achieve this state. Long-distance runners refer to it as "runner's high."
The sensitive, careful and methodical application of pain can move the pain threshold higher, enabling the bottom to tolerate higher levels of pain, thereby receiving the benefits of higher endorphin levels. To the bottom, the pain will not seem to increase, even though the physical trauma upon the body does. This is because as endorphin levels rise, the pain becomes deadened.
Safety Note: The fact that the pain is deadened must never make you lose sight of the physical trauma you are causing. Don't abuse your responsibility for your bottom's safety just because the euphoria of a endorphin rush makes your bottom a little giddy.
In order to stimulate the release of endorphins, the top should gradually increase the pain level until it nears the pain threshold. After reaching the threshold, lower the intensity and allow the endorphins which the pain released to work their magic, nullifying the pain. When the top once again begins to increase the pain, the endorphins which the previous cycle released allow the bottom to tolerate a higher level of pain. The now higher level of pain releases even more endorphins, and the cycle begins again .
Patience is a virtue here. There are several difficulties you may run into. They can discourage you, but don't let them! Keep them in mind, watch for them, and when they occur, alter your technique until you find that unique formula that works for you and your bottom. Sometimes subtle changes in technique can produce dramatic results.

Sometimes the pain threshold will hit a plateau, refusing to rise further. If this happens, a complete break in activity for a few moments, a few minutes or longer might be in order. Every bottom has a certain point beyond which even the best technique cannot take them. This point can vary from day to day. Just because the bottom hit a new high yesterday doesn't mean he or she will hit it again today. If you try every technique you can think of to get beyond the plateau, but to no avail, it's just not the right day. Accept what comes.
Another common problem is hypersensitivity, which causes the pain threshold to drop dramatically. Those of you who have had large tattoos done know how it works. Believe me, it's no fun. You are playing, having a great time - the bottom is on a major endorphin high and you're loving it. Suddenly the bottom safes out. You take a break and then get back into it, but after the break even love taps are too painful. What went wrong?
Hypersensitivity seems to happen most often when you have been pushing too far, too fast. Playing right around the threshold is physically and mentally stressful, and too much of it will wear the bottom out. Make sure when you bring him or her back down, you leave plenty of time for rest.
Endorphin highs are a great reward, but they take hard work. If you are not successful after a few attempts, don't give up. Even an experienced player takes time to learn a new bottom, and as a novice you have to learn the bottom while learning the technique. Just work slowly, stay determined, and look for small signs of success. These small successes will tell you what works for the bottom. Eventually, with patience, you will get it.