Just as a pure rainwater when falling from the sky contacts the earth and is muddied, so the pure spirit soul, when coming in contact with the three modes of material nature, becomes "muddied" by material nature and absorbs itself in various material designations that have nothing to do with the real self. Devotional service, however, clears the mud - and the consciousness - and allows us to see ourselves in our natural relationship with Krishna.
Lectures from a Disciple, Vol.2, Purpose of Sadhana-bhakti