CC Antya 20.52
tāṅra sukha — āmāra tātparya
more yadi diyā duḥkha, tāṅra haila mahā-sukha,
sei duḥkha — mora sukha-varya
Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura says that a devotee does not care about his own happiness and distress; he is simply interested in seeing that Kṛṣṇa is happy, and for that purpose he engages in various activities. A pure devotee has no way of sensing happiness except by seeing that Kṛṣṇa is happy in every respect. If Kṛṣṇa becomes happy by giving him distress, such a devotee accepts that unhappiness as the greatest of all happiness. Those who are materialistic, however, who are very proud of material wealth and have no spiritual knowledge, like the prākṛta-sahajiyās, regard their own happiness as the aim of life. Some of them aspire to enjoy themselves by sharing the happiness of Kṛṣṇa. This is the mentality of fruitive workers who want to enjoy sense gratification by making a show of service to Kṛṣṇa.