Sadly, when trust is broken, some people can't ever get over it. The guilty party has to be willing and able to earn that trust again and the wronged person must forgive and be open to trusting again or it isn't worth it.
@hlpflwthat ,and from what I've seen, sometimes the couples do stay together for various reasons but never recover and live those lives of quiet desperation.
You can't as that betrayal cuts right through you. You can only accept that everything happens for a reason even if you can't see it now. Then someday you can look back and be grateful for what you learned.