Though I'm not under any illusion that neither one, nor both didn't get any 'strange' before or after they were married. In my book, faithfulness is more like two people who run a long distance race together.  It's not a matter of whether one person or both stumble or fall, but rather whether both people cross the finish-line together. It use to be that unfaithfulness by a partner was something that could be worked through. Now days, it seems, more people than not, look at it as an automatic reason to dissolve the relationship.