SB 1.6 - Mixed bhakti and pure bhakti
By practicing self restraint by the yoga system one can get relief from the disturbances of desire and lust but this is not sufficient to give satisfaction to the soul, for this satisfaction is obtained by service to Mukunda (mukunda sevayā). Nārada says that devotional service to the Lord is more effective and practical than artificially trying to control the senses. Viśvāmitra fell victim to the beauty of Menakā, but Haridāsa Ṭhākura could not be seduced by māyā herself. Without devotional service, neither the yoga system nor dry philosophical speculation can ever become successful. In the past many yogīs achieved the platform of devotional service by offering all their endeavors to the Lord and achieved perfection. And the stage of jñāna without the bondage of karma is not glorious if it is devoid of bhakti.
When bhakti is mixed with yoga or jñāna it is called mixed devotional service. Pure bhakti without any adulteration is the foremost means to attain self realization. There are three types of bhakti: pure bhakti (kevala), mixed bhakti but with bhakti being predominant (prādhānya) and mixed bhakti but with bhakti being secondary (guṇa-bhāva). Kevala-bhakti is illustrated in verses 1.5.17 and 1.5.23. Prādhanya bhakti is illustrated in 1.5.36: when those engaged in karma perform those activities according to the instruction of the Lord, they also chant and remember the qualities and names of Kṛṣṇa. Guṇa-bhāva bhakti is seen in 1.5.35: that jñāna which arises from karma which is pleasing to the Lord because of being offered to Him is endowed with bhakti.
Kevala-bhakti practiced by a person who is niṣkāma, also called as ananya-bhakti, śuddha-bhakti, nirguṇa-bhakti, uttama-bhakti and akiñcana-bhakti, gives prema as a result. Prādhanya-bhakti, classified as karma-miśra-bhakti, jñāna-miśra-bhakti, and yoga-miśra-bhakti and practiced by those who are śānta, produces rati (bhāva) and liberation for some. If these persons get the association of a person with dāsya-bhāva or other sentiments, because of the predominance of bhakti desiring dāsya or other sentiments, that person will achieve prema with a prominence of aiśvarya mood. In guṇa-bhāva bhakti, bhakti does not reveal its own results. It is only an assistant to karma, jñāna and yoga which cannot produce results without bhakti. And when mixed with bhakti, they produce liberation.