While you may not have slept the night before (or for an entire week prior to your speech), your audience doesn't know it. They are simply looking forward to what you have to share. The truth is that most people can't tell that you are nervous or afraid. And if you do show signs of anxiety by stammering or forgetting what you were about to say, recognize that your audience is pulling for you. Most people don't enjoy watching a train wreck. There's nothing wrong with saying, "I forgot where I was going with this." A polite audience member will probably gently remind you, and then you may continue.