I haven't been doing school/library presentations for very long but in the very beginning, I'd stress out a little a lot when I thought about standing in front of an audience. That is until my husband looked me in the bulging eyes one day and said something that helped ENORMOUSLY. It was simple but it was magic. He said: just tell your story.
*Mind officially blown*
So, if you're sitting there reading this and you've got a visit coming up that's causing your heart to palpitate, relax and simply tell your truth. Tell your story.