Walter Cannon, physiologist, says that the human body responds physiologically to a wide variety of stressors. One of these is the fight or flight response. To prepare for a fight or flight situation, the body uses energy stored as fat and sugar. The sympathetic nervous system also triggers the release of cortisol, which is a powerful stress hormone.
People perceive events around them as being harmful and will experience stress. Others will not. The meanings we assign to these events are what trigger our stress reactions. Stress is in the eyes of the beholder. We interpret environmental events differently and assign different meanings to them. Stress is not always about what happens, but how we respond.