Spiritual feelings of happiness and intense ecstasies have no mundane comparison. Therefore it is very difficult to give expression to such feelings. We can just have a glimpse of such ecstasy in the words of Śrī Nārada Muni. Each and every part of the body or senses has its particular function. After seeing the Lord, all the senses become fully awakened to render service unto the Lord because in the liberated state the senses are fully efficient in serving the Lord. As such, in that transcendental ecstasy it so happened that the senses became separately enlivened to serve the Lord. This being so, Nārada Muni lost himself in seeing both himself and the Lord simultaneously.
(Srimad Bhagavatam--------1:6:17---------purport).

The exchange of spiritual happiness between Kṛṣṇa and His devotee in which Kṛṣṇa is controlled by His devotee is compared to an ocean of nectar into which the devotee and Kṛṣṇa plunge. This is the verdict of learned scholars who appreciate Kṛṣṇa's opulence.
(Sri Caitanya Caritamrta-------2:19:229--------translation).

If one's hairs do not stand on end, how can the heart melt? And if the heart does not melt, how can tears of love flow from the eyes? If one does not cry in spiritual happiness, how can one render loving service to the Lord? And without such service, how can the consciousness be purified?
(Srimad Bhagavatam--------11:14:23-------translation).

Happiness derived from pure devotional service is the highest, because it is eternal. The happiness derived from material perfection or understanding oneself to be Brahman is inferior because it is temporary. There is no preventing one's falling down from material happiness, and there is even every chance of falling down from the spiritual happiness derived out of identifying oneself with the impersonal Brahman.
(NECTAR OF DEVOTION).

It is said in the scriptures, brahma-saukhyaṁ tv anantam: spiritual happiness is unlimited. Here it is said that even the Lord cannot measure such happiness. This does not mean that the Lord cannot measure it and is therefore imperfect in that sense. The actual position is that the Lord can measure it, but the happiness in the Lord is also identical with the Lord on account of absolute knowledge. So the happiness derived from the Lord may be measured by the Lord, but the happiness increases again, and the Lord measures it again, and then again the happiness increases more and more, and the Lord measures it more and more, and as such there is eternally a competition between increment and measurement, so much so that the competition is never stopped, but goes on unlimitedly ad infinitum. Spiritual happiness is ānandāmbudhi-vardhanam, or the ocean of happiness which increases. The material ocean is stagnant, but the spiritual ocean is dynamic. In the Caitanya-caritāmṛta, (Ādi-līlā, Fourth Chapter) Kavirāja Gosvāmī has very nicely described this dynamic increment of the ocean of spiritual happiness in the transcendental person of Śrīmatī Rādhārāṇī, the pleasure potency of Lord Kṛṣṇa.
(Srimad Bhagavatam--------2:6:36---------purport).

The difference between material and spiritual enjoyment is that material enjoyment is limited. Even if a man engages in material sex enjoyment, he cannot enjoy it for long. But when the sex enjoyment is given up, then one can enter spiritual life, which is unending. In the Bhāgavatam (5.5.1) it is stated that brahma-saukhya, spiritual happiness, is ananta, unending. Foolish creatures are enamored by the beauty of matter and think that the enjoyment it offers is real, but actually that is not real enjoyment.
(Srimad Bhagavatam--------3:20:35---------purport).

The oneness of understanding that the Supreme Lord is fully spiritual and that in full spiritual realization one can understand what He is—the Supreme Personality of Godhead—is called kaivalya, or, in the language of Patañjali, realization of spiritual power. His proposal is that when one is freed from material desires and fixed in spiritual realization of the self and the Superself, that is called cit-śakti. In full spiritual realization there is a perception of spiritual happiness, and that happiness is described in Bhagavad-gītā as the supreme happiness, which is beyond the material senses.
(Srimad Bhagavatam--------3:21:12---------purport).

Devotees of Lord Viṣṇu may aspire for a position in Vaikuṇṭhaloka, but a devotee of Kṛṣṇa never aspires even for the facilities of Vaikuṇṭha; he wants to return to Goloka Vṛndāvana and associate with Lord Kṛṣṇa in His eternal pastimes. Any material happiness is like water in a ditch, whereas the spiritual happiness eternally enjoyed in the spiritual world is like an ocean of nectar in which a devotee wants to swim.
(Srimad Bhagavatam--------6:12:22---------purport).

The real purpose of life is to go back home, back to Godhead, and live with the Supreme Personality of Godhead, play with the Supreme Personality of Godhead, dance with the Supreme Personality of Godhead and eat with the Supreme Personality of Godhead. These are different items of ānanda, spiritual happiness in spiritual variegatedness. Even though one may come to the platform of brahma-bhūta (S.4:20:30) and understand his spiritual identity by speculative knowledge, one cannot enjoy spiritual life without understanding the Supreme Personality of Godhead.
(Srimad Bhagavatam--------8:24:52---------purport).

The word saṁsāra refers to attachment for one's body, home, husband or wife, and children, but although the gopīs and all the other inhabitants of Vṛndāvana had the same affection and attachment for husband and home, their central affection was for Kṛṣṇa in some transcendental relationship, and therefore they were guaranteed to be promoted to Goloka Vṛndāvana in the next life, to live with Kṛṣṇa eternally in spiritual happiness. The easiest way to attain spiritual elevation, to be liberated from this material world, and to go back home, back to Godhead, is recommended by Bhaktivinoda Ṭhākura: kṛṣṇera saṁsāra kara chāḍi' anācāra. One should give up all sinful activities and remain in the family of Kṛṣṇa. Then one's liberation is guaranteed.
(Srimad Bhagavatam--------10:6:39-40---------purport).