Breathing is a key aspect when trying to reach your best results when training and because breathing is due to the lungs movement a involuntary process most people fall into breathing patterns. This involuntary process can tho become voluntary due to controlling your breathing techniques.
A lot of people don't use the full capacity of there lungs when working out and fall into a variety of breathing patterns such as taking in deep breaths then breathing even harder out when running for example, or holding there breath and get angry to do more press ups or a pull ups or bench press's.
This can have a negative effect on desired results or not allow you to reach your potential so developing breathing techniques is a way to do so.
Oxygen is needed for you cells to respire and for energy and when we breath in we breath in oxygen and breath out carbon dioxide (waste) so when excerising control your breathing. Breath in through your mouth (as this is the biggest air passage) as much as possible then out through your nose which is smaller keeping in the oxygen that you need and only getting rid of the waste not waste and oxygen. Use this same technique when pushing yourself to your limit, for example when doing a push up instead of holding your breath and getting angry breath in on the push up then out on the push down so your breathing should match your movement.
Practice this technique at home then slowly but surely implement it into your training and you should see some results.