Happiness is possible only in a relationship with a partner. Imagine that some fellow who has lived his life as a singer goes to an uninhabited island and sings as loudly as possible. If there is no one there to hear him, he will not be happy. To realize that we exist for the sake of others is the great achievement that changes our lives. When we realize that our life is not ours alone but is meant to be for the sake of the other, we begin to follow a path different from the one we were on. Just as singing to yourself will not make you happy, there is no joy without a partner. Even the smallest and most trivial thing can bring you happiness when you do it for another.