Breathing and your life is connected. When breathing is not proper it gets manifested in the life in a negative manner. For instance if you are angry then the breathing is erratic and fast. when you bring your breathing to normalcy then your anger also vanishes.
Watching the breath or controlling the breath is called as swara yoga. This science is has been in India from times immemorial where the time and breath or connected. the time in the terms of tithis and breath in terms of ida, pingala and sushumna. Swara yoga connects this two. so for a particular tithi on a particular time the breathing should either happen in ida or pingala. Also swara yoga says that flow of breath will change for every 1hour 50 min or approximately 2 hrs. when your breathing is in tune with time then whatever you do will be sucessful and will make you highly competent.