Theory behind improved relationships?

I think I’ve heard Brooke say that we should list the things that we’d want our spouse, for example, to do (our manual for them), notice how we’d feel about them if they’d behave in that way, and then feel those emotions on purpose and interact with our spouse from THAT feeling-space (regardless of whether they actually behave the way we wish or not).

This is corollary to “their only purpose is for you to love them,” yes?

This feels right at a gut level, but how does one explain that this improves relationships? Is the theory that when we don’t NEED for another person to change or behave a certain way, the pressure is off, and they can simply relax and be who they are…. And then we ourselves focus on our own thoughts and feelings and meeting our own needs and not making our feeling-state anyone else’s fault, and choosing to feel good and enjoy our lives regardless of what anyone else is doing….

And if so, then is the theory that it really doesn’t matter who our friends are or who we’re married to because we should be able to enjoy our life equally regardless of who surrounds us… and therefore it all comes down to choosing who we WANT to spend time with, only because we want it and not because of any other ‘reason’?

Thank you!