Have you read the thread by etaoin in the Surviving Infidelity bulletin board? You should. It is quite triggery, just warning you.
According to Etaoin, a WH, The WS knows what they have done. If they don't understand the destruction they are causing, they eventually will. They have to live with the guilt and have to live a facade every day. Every day, they expend a great deal of energy building a narrative that supports their actions. So I ask again: How can someone like that be happy?
Happiness comes from a life lived well. AND YOU ARE DOING IT.