Kṛṣṇa is addressing Arjuna puruṣarṣabha, the best of the men. "O the best of the men." Certainly, Kṛṣṇa (Arjuna) is the best of the mankind. Because he is directly friend of Kṛṣṇa, who can be better man than him? The best of the men. So the best of the men, why he's distressed in executing his duty? Therefore this very word is used that, "You are the best of the men."
Actually, the best of the men should not be disturbed by any material condition. He should discharge his duties. And what is the duty? Duty is to become immortal. This is the duty. The lowest of the men does not know how to become immortal, amṛta. Mṛta means death, and amṛta means no death. The modern rascal civilization cannot understand that there is possibility of becoming immortal. They have taken it, accepted it: "Well, who can stop?" They are simply scientifically calculating that, "Some day will come, by science, we shall be immortal, there will be no death."
The formula is given here by Kṛṣṇa how to become immortal. That means you should be callous of this so-called happiness and distress of this material world. That is the first qualification. One who doesn't care what is the distress and happiness of this body, he must execute Kṛṣṇa consciousness. That is the qualification. "Oh, I cannot execute Kṛṣṇa consciousness because there are so many inconveniences," he's not fit for becoming immortal.
People do not know that there can . . . we can become immortal. Immortal we are, but we have been embodied in this material body. Therefore we have to accept mortality, birth and death. These things stated in the Bhagavad-gītā.