प्राणायामं ततः कुर्यान्नित्यं सात्त्विकया धिया । यथा सुषुम्णानाडीस्था मलाः शुद्धिं प्रयान्ति च ॥ २.६ ॥

prāṇāyāmaṃ tataḥ kuryānnityaṃ sāttvikayā dhiyā । yathā suṣumṇānāḍīsthā malāḥ śuddhiṃ prayānti ca ॥ 2.6 ॥

Therefore, prânâyâma should be performed daily with a sâtwika buddhi (an intellect free of rajas and tamas, free of either activity or laziness) so the yogi can cleanse the sushumnâ of impurities - this is a method of performing prânâyâma.