yaṁ hi na vyathayanty ete
so ‘mṛtatvāya kalpate
Translation: O best among men [Arjuna], the person who is not disturbed by happiness and distress and is steady in both is certainly eligible for liberation.
Purport: Anyone who is steady in his determination for the advanced stage of spiritual realization and can equally tolerate the onslaughts of distress and happiness is certainly a person eligible for liberation. In the varṇāśrama institution, the fourth stage of life, namely the renounced order (sannyāsa), is a painstaking situation. But one who is serious about making his life perfect surely adopts the sannyāsa order of life in spite of all difficulties.
Arjuna argued that religious principles should be given more importance than politics or sociology, but he did not know that knowledge of matter, soul and the Supreme is even more important than religious formularies. And because he was lacking in that knowledge, he should not have posed himself as a very learned man. As he did not happen to be a very learned man, he was consequently lamenting for something which was unworthy of lamentation. The body is born and is destined to be vanquished today or tomorrow; therefore the body is not as important as the soul. One who knows this is actually learned, and for him there is no cause for lamentation, regardless of the condition of the material body.