Interesting topic, this is my take on it.
I think that building & maintaining a relation with a partner/children is, for most people, hard enough these days.
Expending time/emotions on an extraneous person is somewhere between unfair & plain wrong.
This board is full of the fallout from such occurrences, but it would interesting to poll MNetters to gauge opinion.
My DW has previously said if I was ever unfaithful, I'd be out. 2 years into our relationship & 5 years before we were married, I took a work colleague out to dinner (we didn't live together before we were married).
Anyway, this girl had a massive rack & I was well, fascinated. So I took her to dinner, had a few beers & then dropped her off in a taxi before going home.
What was I thinking? I honestly had no intention of bedding her (or trying to), but you know what, this is where it starts. In my head, innocent enough, but well on the slippery slope. There was that buzz you get.
A few weeks later, my very shrewd then GF (ladies, you have this talent for logging seemingly irrelevant snippets) took a conversation about the price of fish around to what I was doing 3 weeks earlier.
Busted. And quite right too. She didn't rant & rave, but tearfully pointed out that I hadn't been truthful.
Wake-up call. I grew some, & grew up.
And there's the nub. It wasn't what I did, she wasn't concerned that I was out to dinner with a much younger girl with a hefty endowment (even with beer involved), but that I was being deceitful. And where would that lead?
Sorry for the ramble, but context you know.