Stress is caused by two things. Primarily it is down to whether you think situations around you are worthy of anxiety. And then it's down to how your body reacts to your thought processes. This instinctive stress response to unexpected events is known as 'fight or flight'.
Stress happens when we feel that we can't cope with pressure and this pressure comes in many shapes and forms, and triggers physiological responses. These changes are best described as the fight or flight response, a hard-wired reaction to perceived threats to our survival. When survival had meant facing immediate and real threats such as confronting a charging elephant, our response has saved lives.
At times of danger, the body's innate intelligence automatically takes charge by triggering a set of changes that bypass our rational thoughts. Priority is given to all physical functions which provide more power to face an enemy or to flee. To understand why stress can have negative impacts on your health, you must first understand the physiological changes that occur within your body during the fight or flight response.