When the yogī regularly practices in this way, in a short time his heart becomes fixed and free from disturbance, like a fire without flames or smoke.
evam abhyasyataś cittaṁ
aniśaṁ tasya nirvāṇaṁ
evam — in this way; abhyasyataḥ — of the person practicing this yoga system; cittam — the heart; kālena — in due course of time; alpīyasā — very shortly; yateḥ — of the person practicing yoga; aniśam — without cessation; tasya — of him; nirvāṇam — purification from all material contamination; yāti — reaches; anindhana — without flame or smoke; vahnivat — like a fire.
Nirvāṇa means the cessation of all material desires. Sometimes desirelessness is understood to imply an end to the workings of the mind, but this is not possible. The living entity has senses, and if the senses stopped working, the living entity would no longer be a living entity; he would be exactly like stone or wood. This is not possible. Because he is living, he is nitya and cetana — eternally sentient. For those who are not very advanced, the practice of yoga is recommended in order to stop the mind from being agitated by material desires, but if one fixes his mind on the lotus feet of Kṛṣṇa, his mind naturally becomes peaceful very soon. This peace is described in Bhagavad-gītā (5.29):
jñātvā māṁ śāntim ṛcchati
If one can understand Kṛṣṇa as the supreme enjoyer, the supreme proprietor of everything, and the supreme friend of everyone, one is established in peace and is free from material agitation. However, for one who cannot understand the Supreme Personality of Godhead, the practice of yoga is recommended.