As a teacher, I imagine that part of my role is being present for my students. Sometimes it is being aware of their emotional state as well as their physical state. The student new to a yoga practice may come in with expectations of stretching the body strongly only to find poor breathing needs to be their focus.
The hyper vigilant student needs greater breath awareness and a slower paced class. They will be the ones who are 3 or 4 movements ahead of everyone else. Instructions may bring the need to justify how that student is doing. Humor may help ease the anxious heart. Students with breathing problems come in all different manners. The perfectionist is perfectly comfortable holding their throughout the practice. Becoming aware of how the mind works around different tasks as a teacher is very important.
The complexity of mouth breathing, chest breathing and engaging abdominals muscle and pelvic floor can be so confusing to just about everybody. Weight lifting and the gym workout use a different breathing pattern. Pilates uses a different breath pattern as well. Then there is the 20 or so different pranayama practices in yoga. Here is where holding the space for the student comes into play.
Yoga is about finding balance and calm. the new student can be anything but balanced or calm. Now the fun begins!