You’re another one who says “we’re all human". That it is such a pathetic thing to say. Yes we are human so we have brains, we hopefully have morals, a sense of what is wrong and right. We are perfectly capable of thinking that being unfaithful is wrong and therefore not doing it.
But the part of our brains which is moral and capable of thinking is not the same part which controls our drive to have sex, which is why many people seem to compartmentalise their lives and do something so stupid and risky that they could lose their family and their home for a shag.
We’re animals and our base desires to eat, sleep and fornicate come from a totally different place to our morals and desire to make others happy.
In the book The Chimp Paradox by Dr Steve Peters, that part of our brain and the accompanying behaviours are referred to as our chimp - and his explanation is that when you haven’t exercised your chimp - ie fed it, had sleep, taken it out to run off some energy, had sex, and put in back in its box, you’re not capable of rationalising, because your body shuts down those responses and is running on pure animal instincts to do all of the above. It’s what causes road rage, when the chimpy response to territorial invasion is to get angry, and it’s why we get hangry, or snappy when we’re tired, as our chimp needs feeding and then normal responses and behaviour go out the window. We try to make a point not to have any big discussions late at night because the chimps take over when you’re tired, and say unhelpful things. Of course we’re all able to override the chimp with more helpful human responses if we take a moment, but for some people that probably comes easier than others.
I do believe that some people have better control of their chimp than
others, but I fully believe that people who cheat on their spouse as one-off are able to compartmentalise it at the time due to their chimp being in the driving seat, having switched off rational thought and consequences until it gets what it wants. Those who have a prolonged affair are a different category as that requires some preplanning, lying and manipulating, which are not chimp traits, but sadly all too common human ones.