In devotional practice, whether the senses are involved or not, the involvement of the mind is a must. It is the mind that must practice sadhana bhakti, preparatory devotion. Through sadhana bhakti the mind gets purified and when it is completely purified, one attains divine love through the grace of the Guru. The Bhagavatam (11.3.31) says: bhaktya sanjataya bhaktya . . . "Preparatory devotion leads to perfect devotion (divine love) through divine grace, guru bhaktya sa milati (Brahm Vaivarta Purana).
We have an eternal relationship of love and servitude with Shri Krishna. Shri Krishna alone is our Supreme Divine Master, and therefore, we have to engage ourselves constantly in His divine service, seva. Sadhana bhakti means to constantly think of this relationship and always remain absorbed in Shri Krishna's loving remembrance. Loving remembrance or visualisation of God is known as smarana bhakti or rupadhyana.
Chaitanya Mahaprabhu explains two types of devotion - anasanga bhakti and sasanga bhakti. In anasanga bhakti the mind is not involved; devotional practice is performed using the senses alone. This is devoid of loving remembrance. In sasanga bhakti our mind gets totally absorbed in practising rupadhyana of the Guru and God. Such devotion is considered true devotion.
Jagadguru Shri Kripalu Ji Maharaj
An excerpt from Rupadhyana - Loving Remembrance, the English translation of Rupadhyana, p. 2-3
Also read the Science of Mental Visualisations, Rupadhyana Vigyan in Hindi
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