I had to stop looking at the external parts of my ex's life that seemed good- marriage, vacations, his whole "new life." The thing is, the inside hasn't changed. He is who he is- an active alcoholic, abusive, incapable of holding down a job, all the negatives are still there, no matter how much he tries to keep the surface looking good.
Just because someone's life doesn't instantly unravel before your eyes doesn't mean that the perfect surface is reality.
People put vacation pix on facebook, updates on how great their life is. No one ever says "The alcoholic who cheated on his wife with me is abusive behind closed doors."
This is where letting go can help you. I had to let go of my hopes that my ex's life was going to fall apart, because that was not a healthy way to validate myself.
I wish I could give you a magic formula and say "do X,Y,Z to heal yourself and everything will be sunshine and roses." But it doesn't work that way. I had to take several BIG steps back and detach, detach, detach. My ex isn't on social media, but I stopped getting updates on him from his family, stopped engaging with him when he called to speak to our son, and practiced mindfulness to stop those obsessive thoughts of him when they invaded my brain. I still haven't found the courage to start dating again. I know I'm not ready for another relationship- we've also been split up for about 18 months, and that just isn't enough time to heal from severe emotional trauma and abuse.