Give your partner the benefit of the doubt. When having a disagreement, think that maybe, just maybe, your partner may have an idea that he or she wants you to consider and is not out just to “get you” or be disagreeable.
Humor helps a lot. The more that you can laugh together or at yourself (not at your partner) the more likely it is that overall good feelings about each other and the relationship will keep you focused on a positive solution.
Stay positive in your conversation. Talk about what you like and want more of rather than what you do not like and want your partner to STOP doing or change.
Above all, keep in mind that the person you are disagreeing with is your life partner. He or she was, and hopefully still is, your best friend. Talk together in ways that show your respect and love.