For me, the measure of any relationship -- romantic, friendship, work, family -- is that when we have a disagreement, can we talk about it thoroughly and openly enough such that we are able to reach a higher synthesis? The ideal synthesis speaks to the relative truth of both of our positions while transcending our prior partial views on the matter. I think we've all had relationships where people come to loggerheads and have to "agree to disagree" (permanent stalemate) or find ways to water each other down through some sort of lowest common denominator compromise (where neither person gets what he or she wants). But those sorts of compromises, don't strike me as sustainable (I suppose they are sustainable in the very very short term but they fall apart in the short, medium, and long term).
For me some of the greatest joys in life come from talking through something in a way that leads to an "aha moment" -- the intimacy of discovering a new higher truth bigger than the one we held before. I've had jobs where my boss and I traded drafts (of grant proposals, press releases, speeches, etc.) back and forth -- and each person's ideas sparked a new burst of creativity and discovery in the other. And I've also had jobs where the boss just had not done his/her (personal psychological) work, wasn't a great writer, or was just a dick -- where each disagreement led to stalemate or a series of lowest common denominator compromises until the draft was incoherent. The same thing happens in friendships, intimate relationships, family relationships, etc. -- some are characterized by heart dialogue and higher synthesis and some are characterized by endless conflict and unresolved disagreement. The higher synthesis relationships make me feel happy to be alive while it seems to me that the endlessly conflicted ones are not really worth spending much effort on because that relationship is not gonna be sustainable for any length of time anyway.
Over time, you can tell pretty quickly who you can riff and improvise with and who you can't. And in the very best relationships, you are doing the dance of thesis, antithesis, synthesis all the time without a lot of conflict or disagreement because you've created enough space (trust + love + communication) for an ever-unfolding dialogue of exploration and discovery.
I guess this makes me a Hegelian (thesis, antithesis, synthesis). [And my boy Ken Wilber borrows this idea from Hegel and adopts it to Buddhism (even though I don't think it has anything to do with Buddhism -- the steps towards transcendence in Buddhism seem to go thesis, antithesis, nothingness, everythingness).] But really it's Marx too -- Marx borrowed from Hegel, believing that the march of history consisted of thesis, antithesis, (higher) synthesis.
For me, one of the best resources for learning how to have the sort of dialogue that can lead to a higher synthesis is the book: Difficult Conversations: How to Discuss What Matters Most.