Bhakti involves becoming free from the attachments of this material world and becoming attached instead to Krishna. One cannot become unattached, for one must be attached to something, but in order to become attached to Krishna or enter into the devotional service of the Lord, one has to become detached from material affection.
Sadhana-bhakti, or practice of devotional service, can be divided into two parts. The first part is called regulative principles: one has to follow these different regulative principles by the order of the spiritual master, or on the strength of authoritative scriptures, and there can be no question of refusal. That is called vaidhi, or regulated. One has to do it without any argument. Another part of sadhana-bhakti is called raganuga. Raganuga refers to the point at which, by following the regulative principles, one becomes a little more attached to Krishna and executes devotional service out of natural love. For example, a person engaged in devotional service may be ordered to rise early in the morning and offers arati, which is a form of Deity worship. In the beginning, by the order of his spiritual master, one rises early in the morning and offers arati, but then he develops a real attachment. When he gets this attachment, he automatically tries to decorate the Deity and prepare different kinds of dresses and thinks of different plans to execute his devotional service nicely. Although it is within the category of practice, this offering of loving service is spontaneous. So the practice of devotional service, sadhana-bhakti, can be divided into two parts-namely, regulative and spontaneous.
Source: A.C. Bhaktivedanta Swami Prabhupada (2012 edition), “Teachings of Lord Caitanya, The Golden Avatara”, Page 178
A.C. Bhaktivedanta Swami Prabhupada (2011 edition), “The Nector of Devotion”, Page 21