Breathing is essential. You need to breathe to live and in sports you need to breathe to perform. And it goes without saying, the more efficiently you breathe, the more efficiently you can perform. To be an effective fighter you'll need to develop strong lungs. To become a fighting machine you’ll need to develop controlled breathing.
Due to the mixed aerobic and anaerobic nature of boxing and fighting, efficiency of breathing can make a huge difference in your stamina and also assist you in staying focused. Two common rookie mistakes during sparring and competition are 1. holding one’s breath in the midst of action and then 2. over breathing or gasping for air in between. The combination of these two conditions will quickly cause fatigue. Additionally, anytime you hold your breath you’re temporarily cutting off the oxygen supply to your muscles, which could invite cramps.