Stress may not be a laughing matter to you. But maybe it should be. Humor is one of the most powerful stress-reducing tools there is. "Just as studies have shown the negative effects of stress on the body, we're now finding that humor has positive effects," says Karyn Buxman, R.N., editor of "Therapeutic Humor, the journal of the National Association for Therapeutic Humor. When you laugh, your heart rate and blood pressure rise -- giving your cardiovascular system a mini-aerobic workout -- then temporarily dip lower than they were before. Your immune system makes more immune cells.

Learning to manage stress isn't just good for your body. It keeps your mind and spirit more youthful, too. With fewer worries to tax your brain, don't be surprised if your noggin becomes more nimble. Under highly stressful conditions, it's simply harder to remember things and to concentrate. When stress hits high gear, you may be unable to retain a sentence that you have just read or remember someone you met minutes before.

Some evidence even shows that high levels of stress may shrink the part of the brain that governs learning and memory. Scientists who studied the brains of people with severe depression and post-traumatic stress disorder found that one part of the brain, called the "hippocampus", actually became smaller when high-level stress kicked in. Some researchers speculate that the shrinkage could result from raised levels of stress hormones called "glucocorticords".

When stress declines, you are more likely to stretch your physical and mental boundaries, suggests Phil Nuernberger, Ph.D., president of Mind Resources Technologies in Honesdale, Pennsylvania.