Translation by Srila Prabhupada: O Arjuna, he is the perfect yogi who sees the true equality of all beings in their happiness and misery by comparison with himself.
Purport: A Krsna conscious person is a perfect yogi. He knows the happiness and misery of every being by personal experience. The cause of a living being’s misery is forgetting his relationship with the Supreme Lord. The cause of happiness is knowing Krsna as the ultimate enjoyer of all the activities of human beings, the Lord of all lands and planets, and the ultimate benevolent friend of all beings.
The perfect yogi knows that the conditioned soul, influenced by the modes of material nature, suffers the three kinds of material miseries because of forgetting his relationship with Krsna, and because a Krsna conscious person is happy, he wants to distribute Krsna knowledge everywhere. Because the perfect yogi goes on proclaiming the importance of becoming Krsna conscious, he is the best benefactor in the world and the most beloved servant of the Lord.
na cha tasman manushyaeshu kascineme priyakṛtamah (Bg. 18.69).
In other words, a devotee of the Lord always looks for the welfare of living entities, and thus he is the friend of every being. He is the best yogi because he seeks not only self-sufficiency but also for others.
He does not hate his friends, living entities. This is the difference between a devotee of the Lord and a yogi who is only interested in self-improvement. A yogi who goes into a secluded place to meditate perfectly is not as perfect as a devotee who tries to make everybody Krsna conscious.
From this verse of the Bhagavad-gita we have to understand that the cause of man's suffering is forgetting his eternal relationship with the Lord. But a Krishna conscious person is called a perfect yogi because he does not forget the Lord even for a moment, and he is aware of the happiness and suffering of every person from his own experience.
A Krishna conscious person knows that a man, influenced by the modes of material nature, forgets his relationship with Krishna and suffers from three kinds of material miseries. Since a Krishna conscious person distributes Krishna knowledge all around, that is, he goes everywhere and preaches Krishna knowledge, talks about Krishna, and thus by preaching Krishna knowledge everywhere, he becomes the most beloved servant of the Lord.
A devotee of the Lord never seeks only his own happiness, but he prays for the happiness of all, that is, he seeks the welfare of all as well as himself. He does not envy or hate anybody. This is the difference between a devotee of the Lord and a yogi who is interested in the advancement of the soul. The yogi who goes into a secluded place to meditate is not as important as the pure devotee of the Lord who preaches Krishna consciousness and tries to make everybody Krishna conscious.
