Monogamy: Mission Impossible?

I believe that people are very capable of monogamous relationships. I've seen living proof of two people that have grown old with each other happily until death. But realistically, I would have to say that our social constructs about monogamy and 'infidelities' are really a lot to ask of humans, being the animals that we are. I feel bad that we judge and criticize each other so easily of the mistakes that we make in life, especially those made in relationships...we're animals, suppressing our natural instincts. A lot of people may disagree with me, and I am not suggesting that people should accept/be polygamous, but what I would hope is that we learn to understand humans and their mistakes a little more...Thanks for listening, sorry if I upset anyone.