Why do we love? Perhaps it is simply human nature to do so, though inconsistently to be sure. It could also be a valuable evolutionary trait that contributes to the social cohesiveness that is so critical for the survival of our species. Perhaps we love because a spark of the divine drives us to do so. Whatever the cause, the fact remains that many of us do indeed love, and regardless of whether we love well or poorly, it is very likely that we will continue to love until we die.
This of course begs another question. Why should we love? Should we love because of divine command? Perhaps because it is valuable to the perpetuation of our species? It is my contention that the answer is largely irrelevant except in the sense that so many of us feel a need to justify even our foundational principles, and that we should love simply because people should be loved. I need no justification for love beyond my observation that being a loving person has made my life of immensely better quality and has brought much good on many occasions to the lives of those I interact with.
Please learn to love more fully and deeply and purely. Not because it is deserved. Not because it feels good. Not because it is rational. Not because you are commanded. Love because it is in fact the best thing you can do for everything in existence.