The real question is not, "Why do we get sick," but, "Why don't we get well?" Put another way, "Why do some people stay well or not get as sick or get well more quickly while others don't fare as well?" Broadly speaking we may say that some people have stronger immune systems than others. In our own lives, we know this to be true; we say, "I got run down and caught a cold." Some people assert, "I don't believe in the germ theory, that microorganisms cause disease." Louis Pasteur, the father of the germ theory, said on his death-bed, "The microbe is nothing; all is the terrain [the host's resistance, our immune system.]" (Of course, the powers that be in medicine were already well-launched on their pharmaceutical path and didn't care what Louis Pasteur said on his death-bed.) This is why the antibiotic strategy of poisoning the bug doesn't work. (A study of ear infections in children found no difference in either the severity or duration of the complaint between those who took or didn't take antibiotics. The only difference was that those who were treated with antibiotics were more than twice as likely to have a recurrence, another earache, in the next two weeks.) Lucky for us there are steps we can take to strengthen our immune system.
Vitamin C and a whole host of nutrients found in a good multi vitamin-mineral supplement strengthen the immune system. For example, the mineral zinc helps white blood cells perform their job of immune defense ten times faster. There are immune-enhancing herbs. Mushrooms are prominent in this regard. Rather than buying these in small, expensive quantities at your healthfood store, go to your local Asian market and buy a large bag of dried shitake mushrooms. (If your Chinese isn't any better than mine, first go look at the small, expensive bag of shitakes they're selling in the Asian aisle at the healthfood store so you can recognize them.) Rehydrate (soak) the shitakes and include them in your meals. Even if they are of a lower quality than what's in those expensive immune-enhancing formulas at the healthfood store (and I'm not sure they are) the fact that you can take hundreds or thousands of times more of them (per dollar) makes them a better value.
Nothing strengthens your immune system like sleep. Take a nap. Go to bed early. Sleep in. Doctor's orders. Rest is a close second. Slow down. Take it easy. Take a load off. If you do, you'll make up for the down time tomorrow or the next day when you're more efficient. Peace of mind is essential to healing and well-being.
Deep breathing oxygenates the body. Oxygen is known to fight many microorganisms and to promote the immune system. Decreased oxygenation of tissues is behind many diseases. There are many types of yogic breathing (pranayama) which can be used for this purpose. The simplest is a long, deep breath in through the nose and a somewhat shorter breath out through the mouth. Gradually deepen and lengthen the inspiration. Controlled breathing is also great for establishing peace of mind; the breath is disturbed during emotional episodes.
Eat like you're sick. Avoid rich, heavy, sweet foods. Let your body use it's strength to deal with the disease rather than your indulgent food choices. Generally decreasing the toxic load frees up a lot of energy for healing.
Exercise, including yoga stimulates your immune system, increasing blood flow, massaging glands, etc. While it is hard to exercise when you're down with the flu, exercise is a great long-term strategy for immune enhancement.
Water, the simplest element, is tremendously therapeutic. Ending your shower with a cold rinse or walking barefoot in the dew or snow help your immunity. Hydrotherapy is the backbone of nature cure. Pure water not only doesn't add to your system's toxic load, but actually reduces it. Drink more water.
Improving your bowel health also reduces your body's toxicity.
Immersion in nature reestablishes your own natural balance.
Meditation, visualization and prayer are great aids to wellness. Visualize yourself (particularly the sites of illness) bathed in a golden, healing light. Study after study has found visualization effective. Rather than opposing the illness, try to understand it. Have compassion on it. What does it want form you? Where did it, or you, "go wrong"?
People have cured themselves from serious disease, like Magic Johnson from HIV/AIDS, through immune enhancement; "all is the terrain."