Think of Laughing as Free Health Insurance

It is seldom indeed that someone "dies of laughter." On the contrary, we are now finding that laughing just might be an important key to living longer.
The old saying "Laughter is the best medicine" is timeless. Even back in the 1700's Voltaire observed, "The art of medicine consists of keeping a patient amused while nature heals the disease."
However it wasn't until much later in history that the scientific community began to take this notion seriously. In 1979 the seed was re-planted when an American journalist, Norman Cousins, released his book, "Anatomy of an Illness as Perceived by the Patient." In it he told the story of how he became ill after returning from a job in Russia. His illness progressed to the point that his doctor diagnosed him with acute ankylosing spondylitis syndrome and informed him he didn't have long to live. Mr. Cousins noticed that the hospital's sterile environment was making him feel worse and decided he'd rather go home, under a nurse’s supervision, and watch videos. He soon realized that watching funny movies made him feel much better and that after 10 minutes of laughing, he could sleep without pain for 2 hours. Miraculously and to the surprise of his doctor, after weeks of watching funny movies and lots of laughing, he regained his health completely.
Most of the scientific community was, of course, skeptical of his claim that laughter helped him recover. However, in 1989, his theories finally received merit when a Swedish doctor, Lars Ljungdahl, published an article in the Journal of the American Medical Association titled "Laugh if this is a Joke." According to Dr. Ljungdahl, a humor therapy program increases the quality of life for patients who have chronic illnesses and laughter can decrease pain directly when patients laugh regularly over a certain amount of time.
Seven years later, in 1996, came more scientific support when researchers, Berk and Tan, performed an experiment that showed a concrete connection between laughter and a person's immune system. It measured interferon-gamma (IFN) levels in a test group before, during and after they watched funny video clips for one hour. The result showed that IFN levels were more active after the group had watched the funny video clips and continued to be more active even on the day after. IFN is known to activate T cells, B cells, immunoglobulin and NK cells; all of which help to kill viruses and regulate cell production in ways that strengthens our immune system.
Back in 1989 Doctor Ljungdahl also suggested that when a person laughs, they receive a healthy and unique exercise; something he called "inner jogging." He cited that laughter exercises inner organs we are otherwise unable to reach. A hardy laugh trains the stomach muscles, facial muscles, breathing organs, heart and diaphragm all at once. Indeed, studies have shown that the heart can beat up to 120 times per minute from a good laugh. 
Ljungdahl's observations on the positive physical effects of laughing gained further support in 2005 when the University of Maryland Medical Center published a study, "Laughter: The Best Medicine", which measured cardiovascular effects when a person watched funny video clips. The results showed that laughing could expand a person's blood vessels up to 22%. That's as much as occurs from aerobic exercise. Thus, for the same reasons that aerobics are good for a person, so is laughter. Expanded blood vessels increases blood flow, which delivers more oxygen to the heart and brain, and also decreases the chance for blood clots.
So now we know. Laughing decreases stress and tension, strengthens our immune system, increases our tolerance for pain, exercises our inner organs and betters the condition of our heart and brain. 
So laugh hardily and frequently. The worse that can happen is you will feel good. The best that can happen is you will live longer!