Dealing with others decisions

A couple of months ago I was congratulating a friend on the arrival of his second child. This week he walked out on his wife and kids and moved in with another mutual friend. They've been having an affair for ages apparently.

I'm so angry. But it really isn't my problem. And inevitably sides and factions are being formed up in our friendship group.

Deep breath and try to avoid getting involved or angry with others about it.