"In the few years since medical men began to understand the mechanism of functional disease, they have been so occupied with telling the bad effects of the wrong emotions that they have neglected to stress that effects of the good emotions. They are just as beneficial to the person having them as the wrong emotions are detrimental.
As a matter of fact, good emotions are the greatest power for your good health that we know of today.
He that is of a merry heart has a continual feast.
The body knows the secret of optimal hormone balance. We do not. But there is one way you have of achieving optimal hormone balance. That is to provide your body with the stimulus of the pleasant and cheerful group of emotions. The 'medicinal' value of the good emotions cannot be over estimated.
The healthy emotions have just as great an effect on the pituitary gland as the stressing emotions do. Their effect is just as powerful in the direction of good health as the effect of the stressing emotions is toward bad health.
The healthy emotions, such as equanimity, resignation, courage, determination and cheerfulness, stimulate the pituitary to produce an optimal hormone spectrum, and effect with far greater power for good health than any drug, or set of drugs that we know anything about."
That verse above is from Proverbs 15:13