Yoga practice is essentially meant for controlling the senses. The central controlling factor of all the senses is the mind; therefore one first has to practice controlling the mind by engaging it in Kṛṣṇa consciousness. The gross activities of the mind are expressed through the external senses, either for the acquisition of knowledge or for the functioning of the senses in accordance with the will. The subtle activities of the mind are thinking, feeling and willing, which are carried out according to one's consciousness, either polluted or clear. If one's mind is fixed on Kṛṣṇa (His name, qualities, form, pastimes, entourage and paraphernalia), all one's activities—both subtle and gross—become favorable. The Bhagavad-gītā’s process of purifying consciousness is the process of fixing one's mind on Kṛṣṇa by talking of His transcendental activities, cleansing His temple, going to His temple, seeing the beautiful transcendental form of the Lord nicely decorated, hearing His transcendental glories, tasting food offered to Him, associating with His devotees, smelling the flowers and tulasī leaves offered to Him, engaging in activities for the Lord's interest, becoming angry at those who are malicious toward devotees, etc. No one can bring the activities of the mind and senses to a stop, but one can purify these activities through a change in consciousness. This change is indicated in the Bhagavad-gītā (2.39), where Kṛṣṇa tells Arjuna of the knowledge of yoga whereby one can work without fruitive results: "O son of Pṛthā, when you act in such knowledge you can free yourself from the bondage of works." A human being is sometimes restricted in sense gratification due to certain circumstances, such as disease, but such proscriptions are for the less intelligent. Without knowing the actual process by which the mind and senses can be controlled, less intelligent men may try to stop the mind and senses by force, but ultimately they give in to them and are carried away by the waves of sense gratification.
The eight principles of sāṅkhya-yoga—observing the regulative principles, following the rules, practicing the various sitting postures, performing the breathing exercises, withdrawing one's senses from the sense objects, etc.—are meant for those who are too much engrossed in the bodily conception of life. The intelligent man situated in Kṛṣṇa consciousness does not try to forcibly stop his senses from acting. Rather, he engages his senses in the service of Kṛṣṇa. No one can stop a child from playing by leaving him inactive; rather, the child can be stopped from engaging in nonsense by being engaged in superior activities. Similarly, the forceful restraint of sense activities by the eight principles of yoga is recommended for inferior men; superior men, being engaged in the superior activities of Kṛṣṇa consciousness, naturally retire from the inferior activities of material existence.