Take four count breath in through your nose... Hold it in for a four count... Exhale while you count to four... Keep your lungs empty to a count of four. Boom. You just learned how to breathe tactically. Next time your heart rate starts screaming and your body goes into panic mode right before the clock starts on "Fran", try breathing. Doing a couple of breathing cycles like this will reduce your heart rate, lower your anxiety and help you maintain control of your body. Although the system is a lot more complicated, your heart's purpose is pretty much to provide oxygen to all your cells. So if your heart is pounding and you aren't breathing well, it's not able to do its job. Take a breath.
It always surprises me when I am doing a workout and someone tells me to breathe. I take a big, deep breath and suddenly feel so much better. Breathing seems like something we shouldn't have to worry about, but time and time again we forget to breathe when it is most important!
When performing repetitive movements, like running, rowing, burpees and thrusters, try to get a rhythm going for your breathing and movement. When you have to take a break, don't fold over at the waist, stand tall and open up your diaphragm and ribs so you can get the largest volume of oxygen possible. Breathe in, breathe out, work hard.