Sankara stresses that yoga does not bear fruit for one who does not practice austerity, that… austerity and self-discipline are practiced in a way that disturbs the mind, they defeat the entire purpose of yoga—to still the mind
Bryant’s commentary establishes austerity as indispensable to yoga while insisting, via Sankara, that its practice must remain gentle enough to preserve mental clarity rather than disrupt it.
, The Yoga Sutras of Patanjali: A New Edition, Translation, and Commentary, 2009thesis