Rouky, The MLCer detached from the relationship and you a long time ago, possibly as much as 2-3 years. So, as you can see, they've had plenty of time to move ahead and not feel any remorse about what they are doing. We, unfortunately, were just smacked in the face less than a year or so ago when they dropped the bomb.
Society has changed a lot since social media has taken hold. Unfortunately, people don't look at "cheating" the way they use to because it is so much easier to do it now and yes, divorce is far easier to obtain these days than years ago. It's very sad to see how things have change, and not necessarily for the better.
You may have a down day today, but you'll feel a bit better in a few days. We all have those days and, yes, you'll find something that you really want to do and will like to do in the days ahead. Be patient w/yourself. Don't try to rush the process. Okay?
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.