If I give a person a chance at all, I don't feel that I can control or delay feelings. Like...I can simply not let them into my life, but once I do, and certainly once I have sex, I feel like my emotions are no longer in my own control. I might feel intensely for someone who has no feelings for me. I may feel a negative "this isn't a good match" feeling that makes me not have sex with the person a second time. I might feel a mellow happiness where loving that person is more like a golden afternoon in a field of wildflowers than it is a raging bonfire. I don't know what determines which thing will spring up, or how to hold off feeling whatever I'm going to feel, or how to switch it on or off. I've had men in my life who deserved the bonfire, and I couldn't manage to strike a spark. To me, all of this indicates that waiting a little bit to proceed with sex is likely a good idea, for reasons of trust and emotional safety, not for reasons of "self respect" or prudishness or manipulation. And I've certainly had men get very attached to me very quickly when I didn't return the feeling. Having both sides line up to form a similar level of emotional attachment? I didn't think it was possible. But with my present loves I feel as though things have just settled into a very comfortable place. I don't think anyone has a bonfire going on. It's more the "golden afternoon" feeling. We all love one another, but not in the "OMG I'D DIE TO PROVE MY LOVE DON'T EVER LEAVE ME I NEED YOU FOREVER" way where you're just totally drunk on the other person's energy and addicted to it like a drug.
It's easy. And happy. And right now that is exactly what I need.
Along those lines though...while I do not believe in forever, and I don't believe in "soulmates" or "the one"...I wouldn't say I necessarily take breakups easier than anyone. If I feel addicted to the person, the bonfire thing, it is like a punch in the gut and it's depressing and it cripples my self esteem. It's rejection, and it's painful as heck. And the problem is, while I might know on some level that people come and go and I won't be alone forever (probably not even for long)...when I'm in that damaged state, I'm not at my best and I'm less likely to be able to find someone new, at least someone new that has any business in my life. The thirstier you are, the harder it is to find that tall drink of water. Even a worthwhile person can become unattractively desperate if they're reeling from rejection. It could be argued that a polyamorous person by virtue of the simple fact that we have more relationships going on, is maybe at more risk for rejection and the suffering that goes along with it, than a monogamous person...except that mono folk are often serial mono and not necessarily with one long term partner.
I'm gonna say how we handle breakups has a lot to do with other factors of our personalities and emotional maturity and emotional resilience, and that will vary whether we are poly or mono.