Why is a mother's love unconditional? Because a mother knows who she is and has a defined relationship with her child. Other relationships we might have in our lives seem to come and go since they are based on give and take or a certain set of conditions and once those conditions are not met, that love, attraction, or bond disappears. Only by knowing our true selves can we love unconditionally no matter the relationship, situation, or context.
But what is our true self? It's hard to discover in this day in age where we have been so disillusioned and buried by such impurities that let alone ourselves, it's hard to figure out what is real out in the world. But, by breaking down our walls of ego and in turn, humbling ourselves, allows us to change our perception completely. If you were to mix a bag of the sweetest sugar with 10 bags of salt, it would be impossible to distinguish between them and the overall taste would still be bitter, but if we were to become small like an ant, we would be able to separate the two eventually.
So, in order to love unconditionally, you must know your true self and knowing your true self means to look within. If God is love and man was made in the image of God, then all it takes is us realizing this truth to discover the real bond that exists amongst ourselves.