Build a relationship the same way you build muscle
Stay with me.
I don’t mean you should try to actually break the relationship. But you need to have those uncomfortable discussions you probably don’t want to have. Leave your ego at the door. Be honest with yourself (and your partner).
Only then will the relationship grow.
There’s a difference between going to the gym 3 times per week, lifting the same weights you know you can do all the time, and going to lift as heavy as possible every time. In both cases, you’re going to the gym as equally as much, but the result of the latter will be much greater.
The same goes for relationships.
There’s a difference between “being” in a relationship, and actually being in a relationship where you focus on growing together.