1. One of you must be sane.
Someone once told me that in a good marriage one partner can occasionally be childish, angry, crazy, or demanding. What's important is that you don't both lose it at the same time. If you're both so upset that you can't think straight, take a break.
2. Respect no-go zones.
The beauty of relationship intimacy comes from knowing each other's vulnerabilities. The danger, then, is that you're each uniquely situated to hurt the other when the going gets rough. No matter how angry you are, don't say that it's true he's just like his father or isn't as smart as your ex. You'll never be able to erase it and something equally stinging may be volleyed back.
3. Don't play psychiatrist.
Few things are as infuriating as someone telling you what you think and why you are doing what you're doing. So don't say "Why do you insist on embarrassing me in front of everyone. I think you enjoy it." Just speak to the impact of your partner's actions on you: "I was really embarrassed when you said..."
--Real Simple Magazine