I believe that the very purpose of life is to be happy. From the very core of our being, we desire contentment. In my own limited experience I have found that the more we care for the happiness of others, the greater is our own sense of well-being.
Given the scale of life in the cosmos, one human life is no more than a tiny blip. Each one of us is a just visitor to this planet, a guest, who will only stay for a limited time. What greater folly could there be than to spend this short time alone, unhappy or in conflict with our companions? Far better, surely, to use our short time here in living a meaningful life, enriched by our sense of connection with others and being of service to them.