In the midst of the ocean, volcanic eruptions can do very little harm, and similarly, those who are against devotional service to the Lord and who put forward many philosophical theses about the ultimate transcendental realization cannot disturb this great ocean of devotional service.
The author of Bhakti-rasāmṛta-sindhu, Śrīla Rūpa Gosvāmī, very humbly submits that he is just trying to spread Kṛṣṇa consciousness all over the world, although he humbly thinks himself unfit for this work. That should be the attitude of all preachers of the Kṛṣṇa consciousness movement, following in the footsteps of Śrīla Rūpa Gosvāmī. We should never think of ourselves as great preachers, but should always consider that we are simply instrumental to the previous ācāryas, and simply by following in their footsteps we may be able to do something for the benefit of suffering humanity.
Bhakti-rasāmṛta-sindhu is divided into four parts, just as the ocean is sometimes divided into four parts, and there are different sections within each of these four divisions. Originally, in Bhakti-rasāmṛta-sindhu, the ocean is divided like the watery ocean into east, south, west and north, while the subsections within these different divisions are called waves. As in the ocean there are always different waves, either on the eastern side, the southern side, the western side or the northern side, Bhakti-rasāmṛta-sindhu similarly has different waves. In the first part there are four waves, the first being a general description of devotional service. The second concerns the regulative principles for executing devotional service, and the third wave, devotional service in ecstasy. In the fourth is the ultimate goal, love of God. These will be explicitly described along with their different symptoms.