Praṇayama is one of the important therapeutic and meditative tools of Yoga. Sage Patañjali in Yogasūtra states (II.52): “tataḥ kṣīyate prakāśāvaraṇam”
Prāṇayama helps overcome the covering over light i.e it reduces Rajas and Tamas and thereby promotes Sattva in a practitioner and attunes him towards his goals. Yoga texts also celebrate the practice of Prāṇāyāma as – “praṇayamaḥ paraṃ tapaḥ” – the greatest among acts of purification is Praṇayama.