Short-term stress triggers the production of protective chemicals and increases activity in immune cells that boost the body's defenses; think of it as having your own personal repair crew. "A burst of stress quickly mobilizes this 'crew' to damaged areas where they are likely to be needed," explains Firdaus Dhabhar, PhD, director of research at the Stanford University Center on Stress and Health.
As a result, your brain and body get a boost. A quick surge of stress can stave off disease: Studies suggest that it strengthens the immune system, makes vaccinations more effective, and may even protect against certain types of cancer. Small amounts of stress hormones can also sharpen your memory. In 2009 University at Buffalo researchers found that when rats were forced to swim—an activity that stresses them out—they remembered their way through mazes far better than rats that chilled out instead.
The key, of course, is balance. Too little stress and you're bored and unmotivated; too much and you become not just cranky but sick. "It's important to pay attention to your stress thermometer," and to stay below the boiling point, explains life coach Ruth Klein, author of The De-Stress Diva's Guide to Life.
Let off some steam: 4 simple ways to achieve stress equilibrium