The basic principle of the living condition is that we have a general propensity to love someone. No one can live without loving someone else. This propensity is present in every living being. Even an animal like a tiger has this loving propensity at least in a dormant stage, and it is certainly present in human beings. The missing point, however, is where to repose our love so that everyone can become happy. At the present moment, human society teaches one to love his country or family or his personal self, but there is no information where to repose the loving propensity so that everyone can become happy. That missing point is Krishna.
In the primary stage a child loves his parents, then his brothers and sisters, and as he daily grows up he begins to love his family, society, community, country, nation, or even the whole human society. But the loving propensity is not satisfied even by loving all human society; that loving propensity remains imperfectly fulfilled until we know who the supreme beloved is. Our love can be fully satisfied only when it is reposed in Krishna. Our loving propensity expands just as a vibration of light or air expands, but we do not know where it ends. If we learn how to love Krishna, then it is very easy to immediately and simultaneously love every living being. It is like pouring water on the root of a tree or supplying food to one’s stomach. The method of pouring water on the root of a tree or supplying foodstuffs to the stomach is universally scientific and practical, as every one of us has experienced. Everyone knows well that when we eat something, or in other words, when we put foodstuffs in the stomach, the energy created by such action is immediately distributed throughout the whole body. Similarly, when we pour water on the root, the energy thus created is immediately distributed throughout the entirety of even the largest tree. It is not possible to water the tree part by part, nor is it possible to feed the different parts of the body separately.
Source: A.C. Bhaktivedanta Swami Prabhupada (2011 edition), “The Nector of Devotion”, Page XV