In its most simplified sense, stress is what you feel when the demands on your life exceed your ability to meet those demands. Your blood type is a critical component in the determination of your ability to meet the demands.
A moderate amount of physical activity on a consistent basis will also tend to reduce the overall stress response. Because of this, exercise is often described as a panacea when it comes to moderating against stress or helping to de-stress. However, this is not always the case.
Everyone has an envelope of tolerance for exercise. Train within the envelope and exercise is a great method for managing or releasing stress.