When someone tries your patience, take the high road and keep your cool. What’s really going on is that everyone wants a good deal, and some might try to get it in ways that are more assertive than others.

Breathe, maintain professionalism and take the lows as par for the course (see point 1). The consumer may not always be right, but you don’t necessarily have to be affected by it. At the end of the day, it’s just stuff, isn’t it?