Yoga Sutra 1.31:
"Sorrow, despair, unsteadiness of the body and irregular breathing further distract the citta."
-translation by B.K.S. Iyengar
...or another translation...
"Suffering and frustration, unsteadiness of body, inhalation and exhalation result from the distractions."
-translation by Maehle
We bring everything that we are with us to the mat. Whatever I'm feeling definitely shows itself in my physical practice. When I'm frustrated or upset, my teacher can hear it in my breath...and I can hear that in the breath of my students as well. One of the most challenging times for me to do a strong yoga asana practice is when I'm genuinely hurting over something. The Ashtanga asana practice requires an amazing amount of openness, putting us in a vulnerable place. It's hard to go there when you're in a moment where you really want to close in and put the armor up. On the other hand, when I have managed it, those have been some of the most rewarding practices.