Under such circumstances, the assumption that you are going to be rational is untenable, but there are some things you can do to help yourself along. The first and most important is to slow down the negotiation and to develop a higher level of self-awareness regarding your emotions. Some people do this naturally, and have a good sense of their emotions in real-time. Many other people are unclear at best about their emotions and have great difficulty identifying what is happening with them at any given time. Fortunately, self-awareness is something you can develop with time, through the simple act of paying attention and writing down what you notice about yourself. With time, you will become more comfortable understanding and using your emotions as you negotiate.