2. Too much stress, however, can be harmful. It may make an existing health problem worse. Or it can lead to illness if a person is at risk for the condition. For example, your body reacts to stressful situations by raising your blood pressure and making your heart work harder. This is especially dangerous if you already have heart or artery disease or high blood pressure. Stress is more likely to be harmful if you feel helpless to deal with the problem or situation that causes the stress. 该段体现了unity，这是因为________。