Throwaway, what a surprise, eh?
First of all, I never technically cheated on an SO, but...
With my ex-wife we had an understanding that it was ok to sleep with others. The hows and whys of that isn't relevant. It worked well, it wasn't the reason we split up.
That said, the above fact turned out to be rather important for my personal development.
To elaborate, I was a bit of an awkward nerd when I was a teenager - Something which lasted up until my ex-wife and I made this arrangement.
When it just started out, I realized that I had endless possibilities at hand, but no idea what to do with them. I didn't want to pay for my sex (I'm destitute as fuck) and I know that being a creep wouldn't really cut it. Dem wimmins see right through you if don't have your act straight.
I was at a loss.
Then, and this is where I need you peeps to chill out, because I know Reddit hates this book and all that it stands for, a close friend of mine asked me, one day if I'd read "The Game"?
I thought he referred to the book version of the Michael Douglas movie. Little did I know.
Anyway, he gave me a TL;DR, and while I was sceptical about the idea of a seduction self-help book (never heard about the concept before until that day), I lent it from him and started reading.
Total. Fucking. Revelation.
I've always been interested in how human interaction works, and the answers and methods mentioned made sense to me.
So I started working on my "game", so to speak. And what a difference it made. It didn't make me a true pick-up artist in any sense of the word, but it opened doors. It probably helps that I'm also decent looking (just a little over average, I'd say). Over the course of the marriage, I had a number of affairs with women - Some of which were married/in relationships, some single.
All that is part of the past, and I still consider myself a "clean" guy in the sense that I've never cheated on anyone, ever.
However, I'm beginning to feel greatly tempted to start again.
Why, you ask?
- Despite being "out of shape" pick-up-wise, I've internalized a lot of the teachings of The Game, which means that I often find myself flirting with random women (sceptics will tell me it's all in my head, but hey, if that makes you sleep better at night...).
- Sex with various partners is really exciting.
- This one will anger some, but I find it very satisfying to bang married women. I suck, I know.
- So many hot women out there. I want a slice of the pie :-D

There are dangers, of course:
- Having my cover blown. I despise long, emotional talks :-/
- Hooking up with a crazy woman. Been there, it sucked.
- Stressful. Yes, it's fun and exciting, but it's also stressful as fuck to have to plan ahead and come up with lies and keep tabs on your phone, facebook and so on all the time. Not to mention actually finding the time. While it does happen, the quickies are not the rule of the day. Often, one has to find a space of several hours to commit to the act.

I have a few possible candidates in mind already.