Why get a massage?
Psychological stress, caffeine, diet and sleep habits factor into how the body responds to/handles pain. Massage works on several levels to lessen/eliminate pain. Massage immediately reduces stress levels. When we're stressed psychologically, our body will directly manifest the stress - tightness or pain in the musculature or joints, mental confusion, anxiety, irritability, release of certain hormones (such as adrenalin or cortisol) which can increase heart rate and blood pressure.
If you're constantly stressed, eventually your immune system will adjust to the constant elevated level of stress hormone in your body and weaken. First, massage normalizes the central nervous system immediately soothing the mind and body. You can't help it. Your body's functions will immediately slow down and calm when it receives directed touch.
Second, massage increases the flow of lymph within the body. This increased flow of lymph (immune fighting white blood cells) will counteract the effect of stress and bolster immune function. These effects combined carry you further into an altered state of consciousness thereby lessening/eliminating any pain the body is perceiving.
Massage also increases the rate blood is circulated throughout your body. When your blood rate increases, so does the number of passes through your kidneys. In other words, metabolic wastes due to normal cell respiration that have built-up in your body's musculature (CO2, lactic acid, ammonia, urea etc.) will be directed into the blood stream so they can be filtered out of your body via your kidneys. Another substance usually present in the blood of chronic pain sufferers is caffeine. Why? Because caffeine, in small amounts, is a pain killer. (Many aspirin based pain killers contain caffeine.)
But like anything good, we usually over due it. Many migraine sufferers, for instance, are addicted to caffeine whether in the form of coffee or chocolate or cola. When excess caffeine is present in our bodies, it acts like a diuretic and depletes the water balance in our cells. You might notice that when you're dehydrated, you get a headache. Through massage, you can increase the rate at which your blood is detoxified of caffeine and metabolic waste byproducts leading to a better feeling/functioning body. (Because of this cleansing effect of massage, you always want to drink at least 16 oz of water after your massage to replenish your water balance.)
So you can see that massage can reduce/eliminate pain on many levels within the body while cleansing and healing both the body and the mind. You can also see why massage is such a beneficial 'preventative care' treatment. Received over time regularly, you're body will 'remember' (our muscles have memory) and develop a learned response to massage. This means that the more you receive massage, the quicker your musculature and nervous systems know what to do with it and the sooner you will notice the beneficial effects. It's little wonder that massage has been used as a healing modality for over 3000 years.