At times, the adjustments required by life events exceed an individual's resources to cope with them. Stress results and the life events are stressors. They pose a challenge, a demand, or a threat. Stress increases when stressors are unpredictable, uncontrollable, of intense magnitude, of long duration, and accumulate. Stress has psychological, physiological, and behavioral characteristics like anxiety, post-traumatic stress disorder (PTSD), and self-medication. Stressors can degrade the immune system, making a person susceptible to sickness (cold or headache). In the first stage of coping, a person appraises the life demands and the resources to manage them. In the second stage, a person uses problem-focused coping to manage the stressor or uses emotion-focused coping to alleviate distress or control emotions. In the feedback stage, a person reevaluates the stressor and the effectiveness of coping.