The whole yoga system, aṣṭāṅga-yoga system—dhyāna, dhāraṇā, āsana, prāṇāyāma, like that—they are meant for only controlling the mind. Mind is the center of sensual activities. The purpose of aṣṭāṅga-yoga is to train up the mind, because the mind is very restless. Arjuna, five hundred years ago, he also appreciated the mind is very restless. So he declined to practice the haṭha-yoga system. He said clearly that "Kṛṣṇa, it is not possible for me to control the mind." In another place in the Bhagavad-gītā it is said, "The mind is the most dearmost friend, and mind is the bitterest enemy." Everyone's bitterest enemy and dearest friend is there. That is the mind. It requires little training.
For training the mind, this yoga system is. Those who are too much engrossed in the bodily concept of life, for them, this yoga system, aṣṭāṅga-yoga system, is recommended by practicing a certain type of āsana and making a type of exercise of the breathing, in this way, prāṇāyāma, dhyāna, dhāraṇā, āsana, prāṇāyāma. But there is another simple method that is recommended in the śāstra. You can train up your mind if you simply keep your mind on the lotus feet of Kṛṣṇa. Kṛṣṇa is here, and you see Kṛṣṇa's lotus feet, and if you practice to meditate upon Kṛṣṇa's lotus feet, Kṛṣṇa's bodily feature, then immediately your mind becomes controlled. Sa vai manaḥ kṛṣṇa-padāravindayoḥ (SB 9.4.18). Ambarīṣa Mahārāja, he was the emperor of the world. He had to manage many political affairs. But he was one of the topmost devotees at the same time. Why? Because. . . About him it is stated in the Śrīmad-Bhāgavatam that he practiced this yoga system, the topmost yoga system. What is that? Sa vai manaḥ kṛṣṇa-padāravindayoḥ: "He kept always his mind at the lotus feet of Kṛṣṇa." And his legs engaged for going. . . He was king, emperor. He had no business to go. But still, he was using his legs to go to the temple. This is this yoga system: you employ your senses. Instead of going to the cinema and standing there for three hours for a ticket, if you engage your legs to come to this temple, it is yoga system. So simple thing. Sa vai manaḥ kṛṣṇa-padāravindayoḥ. Instead of thinking some beautiful woman or beautiful man, if you think of Kṛṣṇa, the most beautiful person, then it is yoga system. So simple.