High Energy Only At Shows

Hello!

I have been having trouble showing my horse. This has always been the case, and I have had her two years, but at this point, I feel that it is not just stage fright, but something bigger. She rarely needs to be lunged at home – or, at least, usually every other week. She is pretty mellow at home, and doesn't worry much.

However, ever since I got her, she has been really high energy at shows. She needs to be lunged three, sometimes four times a day. She will buck and kick, which she has never, ever done at home. She sometimes refuses to walk or woah.

I'm wondering what this is from. She has been to about... thirty shows, maybe forty, and every place it is the same thing. She is the calmest horse at the barn, but take her to a show, and she is the first one to flip out. Her diet doesn't change. Her feed times don't change. Her tack doesn't change.

What is going on?