Stress is a reaction of a person's body and mind to varying challenges and demands. Stress helps your body get ready to perform, and that is why stress can be a good thing. Stress can also be a bad thing, so the key to stress is stress management.
Stress and anxiety are often used together, so sometimes people think that stress and anxiety are the same thing. They are related, but there is a difference. One key feature of stress is that it is caused by a stressor. Stressors can be biological, environmental, cognitive, behavioral related, and/or life situations. Environmental stressors can be things like noise, pollution, and crowding. The life situation stressor is probably one of the most common. Maybe you are stressing about an upcoming test or stressed about relationship trouble. Perhaps you have a major deadline coming up at work, and you are not sure if you can make that deadline. It could even be a family member who is sick, and you are stressed and worried about whether or not they will overcome the illness.
When a stressor is present, your body's stress response kicks in. The first stage of the stress response is the alarm stage. During this stage, the body is flooded with adrenaline and gets itself ready for fight or flight. Pupils dilate, breathing rate increases, heart rate increases, muscles contract, digestion slows/stops, and veins constrict. These are all short term effects of stress. Headaches and nausea are also short term effects of stress. Perhaps you've felt "sick to your stomach" before giving an important public speech or playing in an important sports competition.
After the alarm stage is the resistance stage. During this stage, the body adapts to the demand and performs at higher levels. It is not possible for the body to maintain this stage indefinitely, so the fatigue stage will soon follow. Sometimes people will call this stage an "adrenaline crash." The fatigue can be physical, psychological, or pathological.
If the body's stress response to specific stressors is effectively managed, then chronic stress can be avoided. Chronic stress can lead to longer term effects of stress, and these are more often than not detrimental to overall health. Chronic stress can lead to psychosomatic symptoms like headaches, muscle pain, high blood pressure, heart disease, insomnia, and a weakened immune system. Other long term effects of stress can be anxiety, mood swings, and depression.
Exercise, music, being social, meditation techniques, reading, and personal hobbies are all forms of effective stress management.