Stress is about how we respond when things don't go according to our expectations. Life is full of interruptions, surprises, and delays. When things occur that are contrary to the individuals’ expectations, the cycle of stress reaction begins. How a person perceives an event or thinks about it in light of his or her values and expectations will pretty much determine how he or she responds or how much stress is experienced. That applies systems theory to the examination of stress.
That aids in seeing the whole and the interaction of the contributing parts.
That has effectively assisted many people over the years in identifying patterns in their behavior.