A 2005 study of middle-aged men and women living in the United Kingdom found that people who are happier in their daily lives have healthier levels of key body chemicals that those who have few positive feelings.   This University College London (UK) study is the first to link everyday happiness with lower levels of the stress hormone, cortisol, and reduced levels of the blood protein fibrinogen, which causes red blood cells to clot and may contribute to coronary heart disease.

"Not only is there a right to be happy, there is a duty to be happy.  So much sadness exists in the world that we are all under obligation to contribute as much joy as lies within our powers." ~ John Sutherland Powell