Stress is caused by the body's instinct to defend itself.
This instinct is good in emergencies, such as getting out of the way of a speeding car. But it can cause physical symptoms if it goes on for too long, such as in response to life's daily challenges and changes. When this happens, it's as though your body gets ready to jump out of the way of the car, but you're sitting still. Your body is working overtime, with no place to put all the extra energy. This can make you feel anxious, afraid, worried and uptight.