How do you control your emotions in stressful negotiations?

In stressful negotiations, I would always try to response properly rather than to react impulsively. You will always end as the winner if you know how to negotiate with a clear head and not let your emotions affect your dealings.

 Thanks

I prefer to let the answers for experts

By exercising, as you should simulate the whole negotiation process or meeting in your brain before you meet the other party which will enable you to prepare the appropriate words, idioms, and emotions besides predicting what you will face in the meeting.

Keep Calm , Listen n listen. Wait for your turn.

In general, I practise autogenetic training for many years. This helps me to regulate myself when required.

As a practical hint: The more others build  presure and try to speed up things, the more I slow down. Apart from a real emergency, you have the right to take your time, e.g. to give a well thought answer instead of a burst (you may regret later).

Take the deep breath and think that success in this difficult negotiation will have more fun and joy than this effort

Stress is a normal reaction in a human nervous system. Lately science has confirmed that stress happens to improve your status or position at that time as certain hormones are pumped at that time.

When facing stress some people become overwhelmed by fear because they dont know how to react about stress

Leave stress do its thing, you should focus on your main task as stress is here to keep you firm then leave again.

Emotions at that time are preffered to be "having a thick or straight face".

When you see yourself in such a stressful negotiation, you have a purpose that brought you to that point, therefore all other inclinations that has to do with the human ''SELF'' or ''EGO'' should be overiden by the drive to get your desire out of the negotiation. At this point, shut the doors of sentiments and open the doors of reasoning to ride on, at this time you will discover your become relax because the doors of reasoning can only remain open when your are relaxed.

If you have an aim on end result or to reach some result you will always keep your emotions in control