Ok, one fairly frustrating occurrence in my life is when my girlfriend gets freaked out about failing a math class. The problem being that she gets about as freaked when she does well on a test as when she does poorly on a quiz. Pointing out that she seems to just want to panic regardless of the event seems to calm her more than most of my other approaches.

But the example I was actually thinking about when I wrote that involved a coworker talking badly of someone else in the workplace. The specifics are lost to me, but at the time, I noticed that the complaining guy would have had material to gripe about regardless of what the other person did. I mentioned this, and he conceded the fact and changed the subject.