If I knew how much breathing impacted your stress, clear-headedness and overall health, I probably would have done a lot better in college.
To my embarrassment, I only found out a year ago that it's unhealthy to breathe through your mouth. (I guess I missed that lesson in school.)
But most of us still manage to over-breathe. You can read all about it in The Oxygen Advantage.
Better yet, when we perform in public, we often forget to breathe altogether.
But when you work on your breathing, a lot of other things become easier. And, there are simple breathing things you can do that dramatically alter your state of mind and being.
Don't believe me? Try this exercise, and let me know what you think.

You know I could talk about the breath all day long! Why is it unhealthy to breathe through your nose?!
Oh, crap! That was supposed to be unhealthy to breathe through your “mouth.” Edited…hopefully I didn’t ruin anyone’s life just now lol.
Thankfully, I’m learning, although still a work in progress, about breathing!! And also thankfully, you remind me to breathe at EVERY LESSON. I think my default, and many other people’s default as well, is to shorten our breaths in times of any level of stress!! So, I’m trying to remember to breathe especially when I sit at my piano bench even at home!! I’m hoping to make it my default at least starting w my piano and maybe I’ll be able to branch out and include it in other aspects of my life!! Who know that breathing was so important??!!! Lol