We all tend to change time passing. Me and the person married 15 years ago are most definitely two different persons today. So marriage is an effort of will to

We all tend to change time passing. Me and the person married 15 years ago are most definitely two different persons today. So marriage is an effort of will to be renewed each day. Children can help as they may strengthen your will to stay together in their interest. Economics have a major role too. If the couple is well off together, this may help too. I think humans are not born to be monogamous, but they have been (poorly) programmed to accept that by religion and society.