I have found that my vocal chords and my throat are like a canary in a cave. If they don't feel right, a cold, flu or other general cootie is generally right around the corner. Does this send panic through me as I set out to sing or act? Yes it does. Does the same issue hold true for public speaking? Yes it does.
After giving a few hundred speeches in the past year, I've been struck by the variety of ways that different people introduce the same speaker. Some introductions energize me and seem to leave the audience excited to hear from me. Other introductions inadvertently make it more difficult to deliver a successful speech.