idk, cuckolding could mean so many different things to different people. some like the humiliation part of it. some like just seeing their partner enjoying themselves. some may be don't feel "worthy" of their partner (small cock, old/young couple, pretty/ugly couple), and while they know it's not ultimately true (if cuckold is done right, i'd say that relationship/marriage is on very solid fundations) they feel good they can "make up" for it. and for some, mix of part or all of above. human mind is weird and beautiful.
how i look at it - it's you overcoming your ego, and let yourself enjoy looking at your partner having such a good time. just be happy for them.
and some people can do this, and some can't. and that's ok.