A stressor is any activity or experience which changes your normal physical or emotional balance.
Stressors can be external or internal.
They include disturbing news, sudden weather changes, arguments with other people, long hard work, financial difficulties, injuries, and major changes such as divorce or loss of a loved one. Stress is the body's response to any demand put upon it. It is your reaction to an event. When you experience stress you breathe faster, your heart rate speeds up, and your blood pressure increases. You feel tense or anxious.