Whenever you face any fear your breathing becomes very shallow. Once your breathing becomes shallow then rest of the organs becomes very tight and results in experience of fear. This is a very common technique you see everywhere. Google on how to conquer fear and you will find this as one of the common technique. Once you get lots of oxygen then your body and mind becomes very calm. Once you become calm you automatically start thinking clearly, calmly and logically. You would also get internal energy to face any challenge and take decision. Also, lot of emotional toxins will get eliminated through breathing. But still I would consider this breathing solution as more like basic and easy step. If you practice breathing regularly then some structural changes will happen and that will give more of impactful benefit. But most often people try to follow these kinds of technique when they face fear. Just doing breathing at the time of facing any fear won’t work much.