When life gives you lemons, make lemonade! Another reason why happiness is important is that the link between stress and illness is very well known and well documented, as is the reverse. Happy, positive feelings change the chemical make up of our bodies, producing chemicals that enhance immunity, cell repair, and building strength. Happiness is the opposite of stress. See the article, Three Research Findings on the Link Between Happiness and Health, for more ways being happy is good for your health.