I have found in my work with couples that what constitutes a betrayal varies from person to person.
For one client finding a text to a work colleague on her partner's phone led to such distress that we spent many months exploring this, and what acceptable boundaries looked like for this couple.
I have also worked with couples where multiple affairs, and or brief encounters, were part of the couple dynamic. I don’t subscribe to the idea held by some Couples Therapists that the ‘betrayed’ partner somehow colludes and unconsciously lets this happen. It is much more complex than that. Often….past trauma and abandonment leads to compulsive behaviour resulting in a constant need from others for attention and validation.
Sometimes affairs prop up a relationship. The affair partner is trying to keep their partnership alive and often acts out in ways that would not be acceptable to their primary partner. These kinds of affairs can go on for a long time, but if one person in the ‘triangle’ wants out the whole edifice collapses.
I am also seeing more clients who want to experiment outside of their relationship with each others blessing. For some clients this means going deep inside themselves to think about age old human emotions like jealousy and insecurity.
I have only briefly touched on a very complex subject. To find out more read:
After The Affair Julia Cole (Relate Publications 2010)
The State of Affairs Esther Perel (Yellow Kite 2019)
Not Just Friends Shirley P Glass (FP Free Press 2003) Particularly helpful on infidelity at work.