I was visiting a friend and her daughter was going to go on a camp out the next day. Her teacher told them that there were wild animals around as a way to get them excited, this freaked her out and she couldn't sleep. I told her that I could help her if she wanted it, she said yes.
"The truth is that at this moment, you are safe. You are home with your family and that at this moment everything was OK. This is really all there is, now, and you are safe and sound. You can even go back to bed and now think about other things that you'd like to think about, or try what I do right before bed is to not think about anything. Tomorrow you will be around many adults and our job is to keep you safe and keep the wild animals away so even tomorrow you'll be safe."
This seemed to work for she went to bed and that was the last peep we heard from her.