I love the stop sign analogy that some people have posted on here before. You, the betrayed spouse, are a stop sign. Your wayward spouse is a drunk driver. The drunk driver gets into an accident and plows over the stop sign in the process. We didn't do anything to deserve this, just like the stop sign didn't do anything to deserve getting hit. Our spouses are the ones who made the choice to drink and get into the car, and hitting us was nothing personal, we were just collateral damage resulting from a series of poor choices. (In my situation, I like to think of the drinking as a porn addiction, and getting into the car and driving drunk as actually acting out on those fantasies). I don't know if that makes any sense or is helpful, but it helps me when I start to take things personally. I get into this rut of, was I not good enough, pretty enough, etc...and I've realized that those questions are just like someone asking the drunk driver "What did that stop sign ever do to you? Didn't you love the stop sign? Wasn't the stop sign good enough or pretty enough?"
Hope everyone is having a good day!