Look at Richard Gere, here is a guy married to Cindy Crawford and then cheats on her with another model. He just wanted to be with another beautiful women.
All men do.
The mental dilemma is not a new one - do I repress what is natural and remove the automatic sexual response to someone who is empirically attractive or do I develop a mental distortion of who I am to fight off these animalistic traits that hurt my mate so much. Can't be done without a concsious effort, which eventually cause a neorsis because of your sexual polarization. You must have that balance in your life - just ask Carl Jung. The important aspect about this subject is the fact the the man is with you. He is still a man even though he is with you.