If you are going to have to see them, sometimes it helps to pretend you are in a movie, and you are a heroine played by Katharine Hepburn. Or Audrey. Or whoever. Not, under absolutely any circumstances Rita Hayworth though, you’ll just be throwing drinks at people and generally behaving badly. I mean, I wish I was Rita Haywoth, too, but you have to do that in private. Try to behave the way this character would behave. Affect and accent. Just for kicks. Do that. They probably would not start screaming that their ex was a shitbag. You can think your ex is a shitbag, but remember that you are acting. You are playing a role. You are speaking Katharine Hepburn’s bizarre accent. The role you are playing is one of a saintly-good person. You’re an actress. Just play a role and then afterwards, when your ex has left and you are in private, you can demand applause from your friends. Your friends will be down with it. They know you’re weird.
It helps, too, to remember that no one is the villain of their own story. Whenever people talk about how they need to hate their ex, they often say something to the effect of “you don’t understand – he fucked my dog.” I’m not pro-dogfucking. I agree that was a bad thing to do from my point of view. But I also realize that no one thinks they are a bad person. Your ex probably genuinely believes that he and Fido had something special. You can hope he does not fuck other womens’ dogs in the future, but you are probably not going to be able to convince him he is a bad person. You’ll never be able to convince anyone of that.
Even if you could, it wouldn’t make you feel better. Not now that he and Fido are getting married.
But what if things were not quite that bad? What if your ex makes an effort to be friends again? What if you find that, after giving yourself enough time to cool down, you think you would still like to be friends with them?