Tea steeped too long gets bitter. So do arguments.

Time does not improve a disagreement past a certain point. The first few minutes carry the real content, and after that you are extracting something bitter: repeating yourself, dredging up older grievances, saying things for effect rather than because they are true. Everybody knows when it has turned. Almost nobody stops at that moment.

Set an exit for your next hard conversation before you begin, and take it when you feel the taste change. Say you want to carry on tomorrow and mean it. Most arguments were finished a long way before they ended.