I'm poly and am now in a monogamous marriage but was in a few poly relationships prior. I'm 99.5% okay with this.

Poly was fun but had high overhead - there's a certain amount of work required for any relationship and it seems to increase to some extent as you get closer with someone. Two partners was literally double the work, sometimes more. A lot of people thought I was a swinger which always pissed me off. A couple of non-poly girlfriends thought it gave them carte blanche to fuck around on the side while I was staying monogamous for them. Classy.

My very last poly partner was simply horrid and ultimately turned me off to poly. Successful polyamory requires trust and communication. We had been unintentionally monogamous for awhile and it turned out she was not communicating some unfulfilled needs. To be fair, they were valid needs, but I couldn't have known to fulfill them without being told first.

When she and I started dating, we were only seeing each other and had agreed that we'd only consider bringing new people to the relationship if our "core" relationship was solid. That was always my condition in every poly relationship. Years later, without any prior warning, she told me about the issues she had with us and mandated that the only way she'd be willing for us to stay together was if I were to support her starting a relationship with an absolute trainwreck of a human being. He was a socially awkward, late twenties, literally virginal fellow that had never been in a relationship of any kind before and he nailed the cocky, oblivious, "kind of an asshole but projects the blame on you" engineer stereotype on the head so hard you could feel it across county lines. I noped the fuck out so hard. Looking back, my ex had glaring warning signs you could see from space, but I was pretty young and nieve, plus I was madly in love with her even before we started dating. This and an earlier relationship with a narcissistic abuser are the only relationships I regret.

I met my now wife a few months after my ex and I split. She didn't want to do poly and I was pretty burned out on it, so I had no complaints. I do miss it sometimes. I'm a bit of a flirt and I really miss that, the excitement of hitting it off with a new person and all the chemistry and interesting things to learn about them. Still, I wouldn't trade what I have with my wife for all the dates in the world.