the stress factor
If we rarely catch a break, our bodies end up in a chronic state of arousal. "We're built for the fight-or-flight response to stress, but we're also built to need time to recover from it," says Heaney. "Doing without that lessens our ability to fight off disease and takes a toll on energy levels and vitality."
Chronic stress leads to a range of debilitating conditions, such as fatigue, irritability, sleeplessness, anxiety, back pain, headache, stomach upset, depression, hypertension and heart disease.
"All work and no play makes us more than dull--it makes us dead," declares Jerry May, Ph.D., a professor of psychiatry and behavioral sciences at the University of Nevada in Reno.
For the last 15 years, May has been studying a group of about 3,000 high-achievers in fields such as business, medicine, law and athletics. He's found that those who incorporate more play into their days aren't just happier, they're more productive, have higher self-esteem and less stress, and they sleep better, among other benefits.