Understand the position of the person you are disagreeing with. Identify the source of the disagreement: is it a fundamental disagreement with your position, or is it a problem in the way you are communicating that leads you so see the problem differently, or could it be that something has damaged your relationship with this person and that is the actual reason for the disagreement.
Research shows that a deep understanding of the opponent can endow a powerful advantage in any negotiation. Adam Galinsky AG Adam Galinsky and colleagues define perspective taking as a “cognitive capacity to consider the world from other viewpoints” that leads to better outcomes in decision-making than empathy (feeling sympathy and compassion for a person).
It can even be helpful to deliberately develop arguments for the opposition like junior lawyers are often asked to do before developing the arguments for their own case. Understanding the opposing point of view serves to stress-test a hypothesis and can help in developing more effective arguments supporting it.