Relaxed abdominal breathing is better. Tight thoracic breathing isn't as good and may lead to problems. When a person becomes anxious, sad, scared, aroused, or angry, the body immediately begins to go through changes in order to cope with the new situation. We increase the amount of air we breathe, by breathing faster and deeper. Our heart quickens its pace, more blood flows through the arteries and veins, our senses become more acute, we become more alert.
Human beings are capable of a great range of emotions and physical responses.
We can be placid like the waters of a gentle pond, or raging like the ocean in a fierce storm. The change from placid to raging can happen in the twinkling of an eye. It's all part of being human, even necessary to being human. Problems arise when the emotional and physical responses can't be played out, when the storm has to be held inside, not unleashed in some civilized or uncivilized way. It is the connection between emotions and physical responses that concerns us when we think about panic attacks.