Then add various #s of people and plan out what you would do.
You have something he/she wants, and he/she has something you want (sex, companionship, etc.) As a result, the both of you benefit each other.
On the other hand, if you had a strong identity outside of the relationship, then you would simply return to the happy state you were in before you made the trades.
You tried a particular trade and it didn’t work out.
Now you’re left with what you started with, but with more experience.
Do you realize that means you’re better off than you were before you entered the relationship? You’re now standing at a point higher than you were at before the relationship (and either higher or lower than when you were in the relationship depending on how you look at it). Now, if a relationship happens to come along which will make you happier – Okee dokie! A lot of pain comes as a result of not knowing yourself and what you want.