I believe no man should marry a woman who is not special enough to him that he will honor his promises to her.

That said, sometimes people are the worse for wear over time, they aren't as attractive, or even as nice ... but at least have the integrity to end the relationship then, so you still have your integrity at least. If so be that the problem is actually that bad. Which, in fact it seldom is.

What some people haven't figured out is that society, especially pop culture, regularly conflates infatuation with love, and people chase around trying to maintain the state of infatuation (technical term: cathexis) when hedonic tone alone will pretty much make that impossible. We see the natural transition of a new relationship to a more mature and stable state, as some kind of failure. This is really just a failure to properly frame it in your thinking.

In other words never marry for the express purpose of being over the moon all the time. It's literally impossible. Learn to give back your projections and let your partner down off the pedestal you have them on.

It's fear.

It's basic human (primate) nature to cheat, provided one thinks one will not be found out. This applies to both sexes.
Love and lust are triggered quite differently.
The real "trick" is in knowing whether or not to ignore the cheating.

I was married for 40 years and never cheated on my wife. Not like I didn't have the opportunities. I take my oaths very seriously.

He's got it backwards, of course. If a man cheats on his woman, it says more about HIM than it does her. Only a dyed in the wool misogynist would spew some crap like this POS. At least he's got the diaper on the worst part of the turd.

Once again, oversimplification. There are guys who never stop looking for sexual adventure (there are women that do that too). There are women who make sex such a burden that it leaves a door open for a sensual and kind woman to pull a man in. We are all human and as such all different. Statements like this are just meant to appease those who feel hurt by a straying man. The facts don't support it.