Dr. Noir here! I still learn a lot from Dr. Lana. Like this: most marriages and intimate relationships are based on the idea of fidelity, a sexual and emotional commitment to be the one and only and only one for each other -- forever.
What we do know is that affairs lead to heartache for some or all of those involved. Even if the brain says it is "understandable," the heart does not. Affairs lead to real broken hearts.