Nothing else matters in this world unless you have your health. And one of the ways that to always insure your health, is through finding happiness and retaining a joyful heart.
Below is a excerpt from a wonderful website that points out just how important being happy is to your physical health. It's followed by the direct link to the site itself.
"Everyone has experienced that sense of well-being and exuberance from happiness and joy. The eyes shine, the cheeks glow, and the heart beats faster. You suddenly seem to bloom. It is an infectious thing as well as a social uplift. Your happiness makes you radiant, yet few realize what chemical changes this emotion causes in your body. There is a powerful chain of glands, the pituitary, thyroid and the adrenals which, when stimulated by happiness, pour their secretions directly into the blood-stream. This combined secretion forms a potent antiseptic and stimulant which was called by the ancients, "the elixir of life." The body under this condition becomes impervious to all disease, resulting in a state of, health and well-being."