The images and thoughts get better with time. Not sure about the betrayal itself. I certainly hope so. But it tears at the very fabric a marriage is built on and destroys the basic assumptions you have of your partner: that they will respect you, honor their vows, not lie, and not stray.
They do. What has been seen can't be unseen, though. You are correct, it more than tears at the very fabric. Betrayal destroys every single thing...and when trust is broken, what do you have?
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.