Talking. I Don't Know When To Stop

I figured something out this morning. My greatest downfall as a conversationalist is for someone to show interest in what I am saying. Then I feel compelled to say more and the more I say, the more I am convinced that I am an expert on the subject, and the more that my listener is convinced that I am not. I would be better off opening with a tremendous introduction and then let the listener draw their own conclusion.