Is there anything else I need to know about being a Unicorn Hunter that can possibly make it seem more hopeless? Did one partner choose polyamory, and the other partner is going along? The relationship is broken and needs to be repaired or discarded. We are really just like Monogamous people, only they got the number wrong.
Certainly, no matter how well you do your stuff, you are only a part of the equation. This can remain an ongoing point of tension. Our Unicorn Hunter couple might set up a rule that they will be Primaries, and U will be a Secondary to each of them. It does mean that every partner is considered when making big decisions. In the same way, couples that have not examined their own relationship agreements tend to assume that their practices around safe sex for instance will be the same with the third person.