(Kadamba Kanana Swami, 18 February 2013, Leicester, England, Bhagavad-gita 4.37)
It is said that when rivers flow into the ocean, the water from those rivers does not affect the ocean, because the ocean itself is so full of water. So Krsna explains that, in the same way, if the heart is full of service to Krsna, full of desires to please Krsna, then there is no space for material desires to settle in that heart. But if the heart is very empty and there is no service to Krsna, no concern with Krsna, then all kinds of desires just find space in that heart. So this is a very important point, a very important meditation.