Athletes know the mind is just as important as the body.
I don't know why, but nerves never have gotten to me. You just gotta now that if you don't win grand champ that it isn't the end of the world, you'll have other shows and other opportunities. Plus when you go to a show you know what to work on at home :)
Follow up.. you want to base your day around being fun so that even if you don't win, it is a positive experience.
After each lesson, jot down what your coach/trainer had you work on. Review those the night before the show.
Be sure you of focused on having fun rather than pinning high. At the end of the day the experience is all that matters.
I like to do visualization the morning of the show. I will sit on the couch for about 5-10 min and visualize (i am a hunter rider) myself riding my course perfectly. I also like to listen to some "pump up" music. I have a playlist with special music for show days.
I haven't done a lot of shows but I find that talking to my friends or my coach helps me a lot because I don't think about the competition and I don't really feel the pressure. You have to tell yourself that you practiced, you trust your horse, he trusts you and that you'll do great. Those are the best advice I could give :)
Well, studies proves that a horse with his head lewed will be calmer so you can learn him to low his head when you touch his nuque and he will be calmer (works on my horse) then you just talk to him calmly. Excuse my english