Stress generally refers to two things: the psychological perception of pressure, on the one hand, and the body's response to it, on the other, which involves multiple systems, from metabolism to muscles to memory. Some stress is necessary for all living systems; it is the means by which they encounter and respond to the challenges and uncertainties of existence. The perception of danger sets off an automatic response system, known as the fight-or-flight response, that, activated through hormonal signals, prepares an animal to meet a threat or flee from it. A stressful event—whether an external phenomenon like the sudden appearance of a snake on the path or an internal event like fear of losing one's job when the boss yells—triggers a cascade of hormones, including adrenaline and cortisol, that surge through the entire body, speeding heartbeat and the circulation of blood to support quick action, mobilizing fat and sugar for fast energy, focusing attention to track the danger, preparing muscles for movement, and more. Lifesaving as the stress response is, it was meant to solve short-term, life-threatening problems, not extended difficulties such as daily traffic jams or marital problems. It generally takes some time for the body to calm down after the stress response has been triggered. Prolonged or repeated arousal of the stress response, a characteristic of modern life, can have harmful physical and psychological effects, including heart disease and depression.
Over the last few decades, a rising tide of studies has demonstrated the value of regularly engaging in activities that blunt the stress response in one way or another, from meditation to yoga to strenuous physical activity. Since the stress response begins in the brain with the perception of danger or the unknown, researchers now believe that the most basic, and likely most effective, way to defuse stress is to change perception of certain types of situations so that they are not seen as stressful in the first place. Studies show that helping people see certain experiences—such as final exams—as demanding rather than dire protects individuals from the corrosive effects of stress while delivering its positive effects, especially focused attention and speedier information processing. Changing the stress mindset not only minimizes the effects of stress, studies show, but it also enhances performance and productivity.