Totally agree with all of this, the idea is how does one allow a person to be themselves and allow each party to live and "Create" the child called a relationship.
Do I have the answer to this? Fuck No. Do I have decades of experience with relationships including one very long one? You betcha. Am I a failure at things? Yep. But you know what there is no success and no failures. There is waking up and trying and doing and not holding another person back.
As for the grass is greener, the realism you talk to is exactly that. It is the same grass.
I will add one caveat I always add, which is if you add expectations and gross assumptions to the other side, you will find the other side is really a green painted gravel and concrete patch.
Live, Love, Communicate. But don't label or assume, if you do ... enjoy the gravel taste in the mouth as you pick yourself up, instead of landing on a fresh moss bed of fine irish, american, or whatever grass you desire.