Rādhā is the beloved consort of Kṛṣṇa, and She is the wealth of His life. Without Her, the gopīs cannot give Him pleasure.
(Sri Caitanya Caritamrta------1:4;218-------translation).

In His spiritual form, Kṛṣṇa enjoys His spiritual energy, and that is the sum and substance of the Rādhā-Kṛṣṇa pastimes. These pastimes can only be understood by elevated devotees. One should not try to understand the Rādhā-Kṛṣṇa potencies and pastimes from the mundane platform. Generally people misunderstand these as being material. When the pleasure potency is further condensed, it is called mahābhāva. Śrīmatī Rādhārāṇī, the eternal consort of Kṛṣṇa, is the personification of that mahābhāva. In this regard, in Ujjvala-nīlamaṇi (4.3) Rūpa Gosvāmī states that there are two competitors in love with Kṛṣṇa, Rādhārāṇī and Candrāvalī. When they are compared, it appears that Rādhārāṇī is superior, for She possesses mahābhāva-svarūpa. Mahābhāva-svarūpa, the personification of mahābhāva, is applicable to Rādhārāṇī only. Mahābhāva is full of the pleasure potency, and it is an exhibition of the highest love for Kṛṣṇa. Rādhārāṇī is therefore known throughout the world as the most beloved of Kṛṣṇa, and Her name is always associated with Kṛṣṇa as Rādhā-Kṛṣṇa.
(TEACHINGS OF LORD CAITANYA).