  It turns out that the key to avoiding the sniffles may not be how often you take your multivitamin, but how often you smile. Studies have shown that when happy people contract a virus, or “catch a cold”, they report fewer symptoms and are less likely to contract the virus.
   Research done by Carnegie Mellon University Psychology Professor Sheldon Cohen found that when happy people come down with a cold, they report fewer symptoms than would be expected from objective measures of their illness. Could their sheer optimism and positive attitude account for this finding? Perhaps, but when Cohen’s study controlled for those variables he found that people who report positive emotions are less likely to catch colds and are also less likely to report symptoms when they do get sick—regardless of their levels of optimism, extraversion, purpose and self-esteem.
  So how can we become truly happy? Sheldon Lyubomirsky and another psychologist, David A. Schkade of the University of California, San Diego, have put their research together into a simple pie chart showing what determines happiness. Half the pie is your genetic set point, which means that we are genetically predisposed to existing in a certain range of happiness on a daily basis. The smallest slice is circumstances (includes money, your job, where you live, and many of the other factors that play into daily life), which explains only a measely 10 percent of people’s differences in happiness! So what on earth is the remaining 40 percent? “Because nobody had put it together before, that’s unexplained,” Lyubomirsky says. But she believes that when you take away genes and circumstances, what is left besides error must be “intentional activity” or anything that can put you in the “zone.” It could be playing a sport, doing yoga, singing, dancing, or anything else that brings you into a state of flow.
  To sum it up, taking the time to do activities that you enjoy improves your happiness significantly and prevents you from catching your roommate’s cold this winter.
Sources: psychcentral.com, Scientific American
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