Story time. Back in HS I met this girl at one of the parties my friends and I were throwing. She was a friend of a friend from a couple towns over and I literally was fixated on her since I saw her walk in, movie type shit, I know. She was super shy so I started talking, we clicked and I ended up basically talking to her the whole night. Apparently her boyfriend was there that night too but we kicked him out because he was a douchebag (he ended up drinking a 40 full of piss/beer mixture).
Anyway, I flirt with this chick for the next few weeks and she's extremely respectful of having a boyfriend. I guess not extremely respectful because she was basically falling for me. But she would never do anything physical with me because she had a boyfriend. I end up moving across the country, chick still has a whole lot of feelings for me, and I was starting to really like her.
She was the type of chick that ALWAYS had a boyfriend, she didn't stay single long because guys would always wanna wife her up. We ended up falling out of touch because I lived 3000 miles away and who gives a shit right? We start texting again for some reason and long story short she ends up flying across the country to come hang out in my city and shit. She was here for like 4 days and obviously we re-kindled and I have zero regrets because the sex was awesome and she was smoking hot and I had waited years for it basically.
Thing is, I was almost certain she had a boyfriend. I consciously neglected to ask, nor did I care. This was almost 3 years ago now, she is still dating this same guy. They will eventually get married and have a life together. I'm not a man of great sympathy, and I don't tend to display or even possess a lot of emotion either. In conclusion, which is basically the answer to the question, it worked out for me well. But I would be lying if I said I don't think about her from time to time fondly, and I would definitely be lying if I said I don't feel bad. I honestly wouldn't give a shit if she was just dating through some meaningless shit. But they're serious, they will absolutely go the distance. I feel a little bit weird knowing that me and my decisions could potentially have a lasting impact on their life. And I've never met the guy.
Oh, icing on the cake. My mom cheated on my dad and I saw how it affected him when I was growing up so I swore I would never put someone through that. I guess I'm a shithole.
TL;DR I have done it, it worked out well for me. But girl is still with guy, and I think about the impact I could potentially have had on the relationship because they're going the distance.