Psychological stress, to a minor degree is necessary for normal alertness and awareness, but excessive stress can have the opposite effect. Stress may be aggravated by a physical illness or by a mental disorder such as depression.
Stress management is the understanding of stress and its symptoms, and the performing of activities that increase relaxation. The changes in the body that produce fatigue are not fully understood. A person naturally feels tired at the end of a stressful day or after heavy physical exercise. A violently stressful situation car crash for instance, produces severe fatigue a few minutes after the event, even if the person is not injured by the accident. If a person does not and sleep properly, important faculties such as concentration and reflexes are impaired. Fatigue also changes a person’s ability to cope with stress. In some persons stress contributes to disorders like diarrhea, migraine, skin eruptions, and even asthma.

Also many authorities believe that stress may have a direct link with high blood pressure and coronary heart disease. There is also evidence that stress has an adverse effect on the immune system. If a person pushes himself or herself to the limits of fatigue, he or she is unable to deal adequately with stress and health suffers.