Hi--so glad this place exists and for all of your generosity in supporting each other and me!

I have a close friend who I love dearly who has BPD. He's gone through a lot and I've tried my best to support him. As long as I've known him, he has felt cursed: that whenever something good happens to him that makes him happy, something bad will happen to someone he loves. To an outsider, it's clear that this is mostly a matter of a few poorly timed events: there are plenty of examples of good things happening without bad things, bad things happening without good things. There have just been enough times when something good happens right before something bad to make it feel like a curse. Whenever someone around him gets hurt, he feels like it's his fault for experiencing happiness and immediately looks for something good that happened to him to have caused it. 

My question is: how do you recommend I talk to him about it? So far I have just said things like "I'm so sorry, I can imagine how terrible that feels, I hope you know that you deserve happiness." I don't want to come right out and tell him "you're wrong, there is no curse, here are X examples." I don't want him to feel like I don't take him seriously or that I think he's crazy. But I also really worry about letting him continue to think about the curse--the result is that he feels he shouldn't be happy and it hurts me to see it.

Any thoughts? How would you like someone to talk to you about this? Have you had success in overcoming anything like this?