Have you ever watched thoroughbreds being led to the gate for a race. They are apprehensive and excited, often difficult for the jockey to control.
Public speaking causes most people some degree of apprehension. Whether speaking to a small group or a large audience, feelings can rise up that are hard to control.
When you get nervous about something you have to do, be thankful. Just like a thoroughbred it’s in your nature to be nervous, but you were made for this. You will get through the feelings and deliver an excellent speech or performance.