When we experience an involuntary high degree stress response, the sensations can be so profound that we think we are having a medical emergency, which anxious personalities can react to with more fear. And when we become more afraid, the body is going to produce another stress response, which causes more changes, which we can react to with more fear, and so on.
People with panic disorder often worry about when the next attack will happen and actively try to prevent future attacks by avoiding places, situations, or behaviors they associate with panic attacks. Worry about panic attacks, and the effort spent trying to avoid attacks, cause significant problems in various areas of the person’s life, including the development of agoraphobia (see below).