What I said in the OP is that if you try to go about polyamory using monogamy values, you will not be successful because those two relationship styles have different ones (which I gave the term mindset). There are naturally other factors that enter in, but for the purposes of this story, trying to do one relationship style using the values and beliefs of the other one is going to lead to problems and to unhappiness. That's really all I've said.

The thesis of this OP is not that polyamory is a relationship style more likely to bring happiness. Some people want monogamy and really make it rich and beautiful, and that's fine by me. Most people aren't up to the work it takes to do polyamory well, really employing all the values of that relational system.

But nevertheless, I still stand by my original thesis, which is that if you try to go about polyamory using the same outlook on relationships and love that you used in monogamy (the ones taught to you by your culture), you will have a bad time of it, and make both yourself and others unhappy because its a different way of thinking about relationships (which for the purposes of telegraphing the ideas around values, beliefs, conditioning, expectations, I and others have termed mindset).

Adjusting ones beliefs to truly and fully buy into the idea that love is an infinite (not a scarce) resource, that communicating all of your wants, needs, and fears, to those you are in intimate relationship with is a valuable and very bonding thing to do, etc., will in nearly all cases lead to greater happiness because this is a way of relating that is more natural to and healthy for the psyches of human beings. And, as I've said many times in the past, in theory people in monogamous relationships could hold all those same beliefs and engage in all those same practices while staying exclusive to each other. But the fact of the matter is, overwhelmingly they don't. Because monogamous marriage as it is widely practiced is a patriarchal structure seated in relationship hierarchy, control, co-dependency, jealousy as a real indication of love and other unhealthy ways of relating to each other. And, this is the way the culture has taught us to go about relating to each other, even though some people rise above that.

So no, saying "I practice polyamory" does not inherently = happiness, but polyamory practices used consistently by anyone, even monogamists, just very well might because they encourage behaviors that have been shown to lead to fulfilling relationships. But that isn't really the thesis of this story that you commented on. But since you've brought it up I'll say, you have to not just adjust your beliefs, but you have to do the work of carrying them through and acting on them. You have to do the self-reflective work, the taking responsibility for your own emotions work, the vulnerability work, the intensive communication work. Anyone of any relationship style who does that will undoubtedly have happier relationships.