I was at the mall this evening and I met him there. We're still good friends, me and my best friend's ex. So we talked about things, mostly about his love life and stuff. It turns out that his girlfriend was around and voilà, he introduced me to his new girlfriend! I called my best friend later on, to tell her every single thing that happened. Apparently she was kind of pissed of by my story. But I told her this: we are grown-up people, he might be your ex and you hate him now, but it doesn't mean that I can't be friends with him.
What I'm trying to say is: be mature and be objective. Try to see everything in a bigger picture, because life is not happen only just around you.