Text 15

 yam hi na vyathayanty ete
purusham purusharsabha
sama-duhkha-sukham dhiram
so ’mrtatvaya 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.

Commentary by Srila Prabhupada  

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 varnashrama institution, the fourth stage of life, namely the renounced order (sannyasa), is a painstaking situation. But one who is serious about making his life perfect surely adopts the sannyasa order of life in spite of all difficulties. The difficulties usually arise from having to sever family relationships, to give up the connection of wife and children. But if anyone is able to tolerate such difficulties, surely his path to spiritual realization is complete. Similarly, in Arjuna’s discharge of duties as a kshatriya, he is advised to persevere, even if it is difficult to fight with his family members or similarly beloved persons. Lord Caitanya took sannyasa at the age of twenty-four, and His dependents, young wife as well as old mother, had no one else to look after them. Yet for a higher cause He took sannyasa and was steady in the discharge of higher duties. That is the way of achieving liberation from material bondage.

Commentary by Sri Visvanatha Cakravarti Thakur

Practicing tolerance with this discernment, the experience of the sense objects will, with passage of time, not give distress at all. When one reaches this state where there is no distress from the objects of the senses, he is qualified for liberation (amrtatvaya).