Think of it as an opportunity for feedback from equine professionals other than your primary trainer instead of a competition you have to win. And of course, take a couple deep breaths whenever you feel yourself getting tense, stay hydrated, and make sure you eat :) Make sure you leave yourself some extra room in your schedule too so that if something doesn't go quite to plan, you're not rushing around at the last minute trying to get everything together.
I think the more you show the more you'll feel relaxed 🙂
Just remember that if you are competing, it's because you have the skills to do so, you and your horse trained for it and you are certainly ready!
The most important thing is to don't pressure yourself too much, you are here to have fun, to have a good time with your horse and your friends 🙂