Being a teacher, I see many wonderful people with fine breathing practices.
I also see wonderful people constantly struggle with their breath, step one of the yoga practice.
After watching practitioners for some years now, I see one hang up with the breath practice showing up often: snorting air, or rather, getting the face too involved with breathing. A deep breath, to those with this issue, seems to be all about flaring the nostrils, shoving the tongue up against the palate, raising or scrunching the eyebrows, lip pressed, jaw clenched, and so on.The breath gets past all that activation, through the natural functions of our sinuses, just to get caught up still high in the chest. With that sort of chest breathing taking hold, the SNS (sympathetic nervous system) is activated and from there, the practice turns into a fight or flight struggle. All of the sudden, the room is too hot, the pose is too long, the flow is not smooth, the music more annoying, and what cue did that teacher just say?! In an active SNS state, the body forgoes growth, stops healing. To promote healing, strengthen the connection of mind and body, breathing to activate one's PNS (parasympathetic nervous system) is paramount. Deep breathing controlled by the diaphragm, also known as diaphragmatic breath, moves the nervous system back into the parasympathetic state, back into the healing. Let your nose be an open gate for the breath to pass through. Try not to snort the breath, which makes the draw of the breath a pulling function of the face distorting, but rather feel the diaphragm initiate the inhale, guiding the pace. Notice how this can soften the face. Your sinuses already do enough work in their subconscious functions! Your sinuses are conical shaped, to give the breath time to regulate better to the body's temperature. Also giving the inhaled air time for cleansing by the mucus. Your sinuses keep you out of danger! We can literally smell trouble! Many other facts about the functionality of the respiratory system are well documented, definitely worth the dive down the rabbit hole.
That's a lot of work, so when going into the yoga room, forcing the nose to do more work in the breathing process seems to put off the connection in the mind body, and pushes the body into thinking that it just has to save your ass. I find letting my nose be open as I control the breath count with my diaphragm, brings about a sense of healing and fulfillment.
Getting my face out of the way of my breathing practice has made a stronger connection into my mental and physical being. So much more of a blissful resting face looking back at me though the asanas.
I hope that this information sheds some light on your practice or confirms with a nod of appreciation to the magic you already know.