Buyer or seller, it's all about the deal. Every negotiation is a process leading to a goal: the deal. Closing that deal depends on, more than any other factor, communication. The road to the deal is laced with obstacles. How your agent communicates with you and the other agent determine whether these obstacles derail the deal, or pass as barely noticed bumps along way.
A problem arises, what does your agent do? Does he act in the best interest of the client by focusing on a solution? Or does he service his own needs by attempting to assign blame? Grousing and the pointing of fingers never solved a problem.
This is crucial as finding fault is to focus on yesterday. An agent acting professionally will move forward, focusing on solutions to keep the process moving forward, toward what eventually will become the deal. An agent looking to the past, focused on finding fault, is not acting in the clients best interest and needs to be questioned rigorously by the client, and quite possibly replaced.
As with a doctor, a client will place inordinate trust in their agent, as is natural. But I believe clients need to be vigilant and watch for signs of what is really a conflict of interest. Agents must not allow a personal issue to interfere with the interests of his client.
Petty resentments and blaming make a deal less likely. Consider the effect these signals will have on the opposite party and their agent. Problem solving is moving forward toward a deal. Communicating those solutions builds trust, engenders a positive relationship with the other party and brings the deal that much closer.
Your agent must be self possessed, calm in a crises, and respond to that crises with a solution. Righteous indignation is a poor substitute for a deal.