Game theory can be used to explain relationships and in essence it’s about each party in a relationship trying to maximize their gains. Using the same principle in the prisoner’s dilemma, two people staying together will yield the greatest gain in the long run. In the short run however, if a person decides to cheat, that person will have even more gain and the cheated will have negative gain. Using K-level thinking, that person cheated on by the initial cheater will now make their next best move. That is to cheat. By doing so, they will be apart and yet this is far worse off than the initial starting point.
This model is overly simplistic and should only be used as a starting premise for analyzing relationships.
Random hookups and parties are like junk food, they feel good in the moment but they suck the day after. Long term relationships are breakfast, lunch and dinner. They are sustainable and provide the optimal gain.
So, before you make a major decision of choosing your significant other, think about the long term. What’s sustainable is the priority. What fades is secondary.