Stress is triggered when a demand, or stressor, threatens to overwhelm your capacity to cope. A deadline, illness, economic insecurity, the comments of others, a setback—any number of things can set off stress. When the response is activated, an ancient part of your brain believes your life is in danger.

That perception may seem very real, but it’s a false alarm most of the time, since most demands are seldom a matter of life-or-death.

“The stress response was designed for another time and place, almost a millennium ago, and doesn’t know how to process the social stresses of the modern world.”

Yet the body reacts as if it really were a life-and-death moment, setting off the stress response, the body’s defense system, and sending the central nervous system into flight-or-fight mode. That unleashes a surge of hormones, such as adrenaline and cortisol, that make your heart beat faster and blood pressure rise. That gives you extra strength and speed in legitimate danger, but it also forces the body to work much harder and taxes your entire system—even when you’re sleeping.

But most of the time it’s a false emergency, one that can be turned off by using the tools of science to manage stress.

Controlling stress is essential, because it’s extremely costly to health, work, relationships, and finances.