Being a mediator, and observing both sides of a conflict, is a privilege.
Through observation rather than engagement, we can see the patterns of behaviours that thwart our attempts at peace and resolution.
One of those patterns is that the outside world (and our negotiation partners) often reflect our internal world back at us.
If you arrive at a negotiation stressed and frustrated then the chances are better than even, that you will see those traits in your negotiation parter (whether they are genuinely there or not). That is because we view the world from the prism of our state of being.
So as always, the answer lies in understanding and controlling our own responses to difficult situations so that we can encourage others to meet us there.
Happy negotiating!