I hate the phrase, "check your [facet of personality]." I have asked people to examine their motivations, and I always will - because saying, "why do you believe you are the most qualified person to give this talk?" should really be answered before the person gets up to speak.

And if the answer is, "I'm not, but the person who is doesn't want to evangelize", fine. But yes, consider why you're speaking. That's fine. Otherwise, the message is a load of drivel.