To address Steve's criticism, I didn't mean to imply that you should always share your state of mind with the audience. Breaking the fourth wall, as it were, can definitely hurt you if you don't know the right time to do so. In my personal example, however, there was no reasonable way to hide the fact that I was perspiring and out of breath, and I would rather the audience not waste its attention wondering why this was the case. So I got it out of the way in 30 seconds and gave a good talk.