You don't know who someone is until you know why that someone is who they are. Which is another way of saying that history reveals the present. The good of marriage is that it gives someone the time to get to know another's history, and in getting to know it they are bound to love them. Indeed this is the good of that relation of which marriage is a subset - friendship. Friendship is not merely the sharing of interests or a sense of humour. It is the sharing of the contingencies that make us who we are. What this means is that constitutive of friendship is nor first of all sameness but difference; not expedience or convenience but the time and care necessary to tell and create a history.
In our so-called global village, however, friendship has been re-constituted. Since we don't have time for history, and since we often find ourselves in places where no one knows from whence we came, it is the superficial that binds us with another. Young people go to college and re-invent themselves, and leave after four years without a self worth remembering. 20-somethings travel around the world to find themselves again, but more often than not they only find themselves without a friend, surrounded by people as selfless as them. The existential quest for self as undertaken in our culture is doomed to fail, because it is undertaken by first of all severing oneself from one's roots, when in fact it is only deep rootedness in time and space that gives one a self in the first place.