As stated by Caitanya Mahāprabhu, the highest perfection in life is to develop one's love for Kṛṣṇa (premā pum-artho mahān śrī-caitanya-mahāprabhor matam idam).
(Sri Caitanya Caritamrta---1:7:84---purport).

This is confirmed in Śrīmad-Bhāgavatam: "If a person worships, adores and loves Hari, the Supreme Lord, he should be understood to have finished all kinds of austerities, penances and similar processes for self-realization. On the other hand, if after undergoing all types of austerities, penances and mystic yoga practices one does not develop such love for Hari, then all his performances are to be considered a useless waste of time.
(Nectar of devotion).

In Goloka Vṛndāvana no one has any desire other than to love Kṛṣṇa.
(Srimad Bhagavatam---5:18:23---purport).

As one advances in devotional service, he attains love of Godhead, and as he advances in this love, he becomes free from all material bondage. One should not think, however, that the disappearance of poverty and liberation from bondage are the end results of love of Kṛṣṇa. It is in relishing the reciprocation of loving service that love of Kṛṣṇa exists.
(teachings of Lord Caitanya).

The word prayojana means "necessities," and the ultimate necessity is explained by Śrī Caitanya Mahāprabhu. premā pum-artho mahān: the greatest necessity for a human being is the achievement of love for the Supreme Personality of Godhead. Here we see that mother Yaśodā is on the highest stage of necessity, for she is completely absorbed in love for Kṛṣṇa.
(Srimad Bhagavatam---10:8:45---purport).

When one's desire to love Kṛṣṇa in one's particular relationship becomes intensified, this is known as pure love of Godhead.
(Nectar of devotion).

If someone remains always attached to Kṛṣṇa, it is to be understood that he is liberated, and his life is successful. With any devotee who loves Kṛṣṇa with his heart and soul, Kṛṣṇa reciprocates in such a way that the devotee cannot but remain attached to Him. The reciprocal dealings of Kṛṣṇa and His devotees are so attractive that a devotee cannot think of any subject matter other than Kṛṣṇa.
(Krsna Book).