This Sixth Chapter of Bhagavad-gītā concludes with this verse, that yoginām api sarveṣām. There are different types of yogīs, but the most important yogī, or the topmost yogī, is he. Who? "Who is always thinking of Me," Kṛṣṇa says. Who is always thinking of God. He's first-class yogī. Yoginām api sarveṣāṁ mad-gatenāntarātmanā. yoga means that: always thinking of God. Dhyānāvasthita-tad-gatena manasā paśyanti yaṁ yogina (SB 12.13.1). The yogī's business is that he's always meditating upon the form of the Supreme Personality of Godhead. That is yogī. Mad-gatenāntarātmanā.
These are the Vedic version, that dhyānāvasthita. Dhyāna means meditation. Dhyānāvasthita-tad-gatena: just being absorbed in the form of God, Kṛṣṇa. One who is meditating, dhyānāvasthita-tad-gatena manasā, mind is so trained up that mind cannot think of anything else except God, that is perfection of yoga. Mind . . . we, our mind cannot be vacant. We must think of something in the mind. Not for a second we can make our mind vacant. That is not possible. So this vacancy, this mind's business—thinking, feeling and willing—when all of them are engaged in the Supreme Personality of Godhead, that is called perfect yoga system, or the topmost yoga system.