When used as a tool for self-transformation and awakening to clearer awareness, yoga starts the moment a student first pays attention to what he or she is doing in the practice.
If a student is unsteady, falling, in pain, or distracted by discomfort, the tendency will be to go back into his or her analytical or agitated mind. Sthira and sukham— steadiness and ease— give the asanas their transformative potential.
Being steady does not mean being perfectly still in a pose that you hold for a very long time. Asanas, by contrast, are alive, in each moment a unique expression of the human being doing them.