Each person has a unique Breathing Resonance Pattern. The place where your breathing matches your diagphramatic breathing pattern and your valsalva wave. Whole books have been written about this. So just do this. Breathe in for 5 seconds, breathe out for 5 seconds. Voila you are breathing at a cyclical rate of 6 breaths per minute. For some people a 5 BPM or even a 4 BPM will be more appropriate. But they are all GREAT. The taller you are the slower the rate you should try out. I am 6' 2" so I breathe at 4 BPM. Seven and 1/2 seconds in and sevent and 1/2 seconds out or 15 seconds for a complete breath cycle, which equals 4 BPM.
Do this 3x a day for a minimum of 5 minutes each time. You will feel better. Your body will undergo a process called autophagy (garbage collection basically), hour cardiovascular system will improve (tryglyecerides down, blood pressure down) and your total health will improve. Do it.