Some studies show up to 70% of all marriages will experience infidelity. This figure I believe is a bit inflated, but I know the rate to be higher than most would think.
I happened to be reading the Catechism today on the Sixth Commandment (“You shall not commit adultery.”) and I read this quote from St. John Chrysostom. It is quoted in #2365 of the Catechism.
(Husband saying to wife:) “I have taken you in my arms, and I love you, and I prefer you to my life itself. For the present life is nothing, and my most ardent dream is to spend it with you in such a way that we may be assured of not being separated in the life reserved for us…I place your love above all things, and nothing would be more bitter or painful for than to be a different mind than you.” – John Chrysostom, Hom. in Eph. 20, 8: PG 62, 146-147.
Perhaps we men would do well to keep this in our wallet and read it daily, then live this out in our vocations.