Getting angry or frustrated with the lawyer on the other side during negotiations doesn’t help your client’s situation. In fact it usually harms their situation and your ability to negotiate strategically or competently. In order to resist being angry it might sound trite to say it, but you need to first notice that you are getting angry or frustrated and then stop talking or stop the behavior that exhibits your anger.
A good rule for you to have is to never say or do anything out of anger.
You’ll need to support your rule with tactics that will help you handle your anger constructively. First quiet your mind and breathe before you say or do anything further.
Then rather than retaliating or escalating the disagreement, decide to take responsibility for your part in the escalation of the exchange. Apologize and come up with a question that can help you get the negotiations on track to the conclusion you’d really like to have happen for you and your client.
For example: You’re right about that point. What is most important to you? or What do you really want to achieve if we agree with your position?