Stress is your body's way of responding to any kind of demand. It can be caused by both good and bad experiences. When people feel stressed by something going on around them, their bodies react by releasing chemicals into the blood. These chemicals give people more energy and strength, which can be a good thing if their stress is caused by physical danger. But this can also be a bad thing, if their stress is in response to something emotional and there is no outlet for this extra energy and strength. Stress that continues without relief can lead to a condition called distress -- a negative stress reaction. Distress can lead to physical symptoms including headaches, upset stomach, elevated blood pressure, chest pain, and problems sleeping. Research suggests that stress also can bring on or worsen certain symptoms or diseases. Stress also becomes harmful when people use alcohol, tobacco, or drugs to try to relieve their stress. Unfortunately, instead of relieving the stress and returning the body to a relaxed state, these substances tend to keep the body in a stressed state and cause more problems.