(Pre-edit: this became much longer than intended. You struck a chord in me it seems.)
You’ve articulated this so very well. It’s a lesson that took me many years to learn and comes with the prerequisite of respecting yourself and respecting your partner to such a degree that the relationship comes second for both of you. Each person’s first priority should be themselves. Both parties need to respect that to the point of accepting that staying together is not a given and is contingent on both parties being fully satisfied with the direction your lives together is heading.
The funny thing is that I’ve never felt more confident in my relationship since learning that. I used to think that’s putting the relationship second to yourself is antithetical to commitment but actually it’s the other way around. The only way to fully commit to a relationship is to make sure that maintaining it is a concious choice rather than an expectation or given.
The way my dad illustrated this lesson in my youth (and I took the advice but only recently learned the full meaning of it) is like this: life is a journey down a road with many crossroads. Should you find a partner, you walk together. If you hit a crossroad and can’t agree on a direction then thank each other for the lovely journey together but let them follow their own path. Find that partner that is going to the same destination and you’ll have found happiness in love.