Typically to get toward a productive outcome in negotiation you have to make the initial move of genuinely exploring someone's model. If you don't, it is unlikely that they will be willing to explore yours. And if you genuinely explore and understand theirs - without judging it - they will be willing to explore yours. Once they reach that point, they are primed to explore the productive combination of both models and won't be as obsessed about trying to make sure their model prevails.