Can you picture your partner as a small child? At that age, he or she was learning how to gain approval from parents, what they liked, what they didn't like. S/he was sometimes hurt by reprimands, criticisms, perhaps even hitting. What did that child do to protect himself? Withdraw? Act out with aggression?
I once had a couple in my office. He had been struggling with her "nagging." Once he realized how hard it had been for her to get attention in childhood, he began to have more compassion. Suddenly he said, "I can never hurt you when I picture you as that little child trying to make sure people paid attention to you."