I walk the course twice, much to the rolling of my trainers eyes, hah. But exposure seems to have been the best thing for me. Just take the time to be confident in your job (walk twice, and start warming up in good time) and the more shows you do the better you'll feel. Also, make sure you eat! Energy to do the job is the thing that makes us doubt ourselves the most
RELAX. That's one of the best things anyone can tell you. If you know you trained, you know your course, and you know your horse, everything should go fine. Don't think about it has a competition with judges and a ton of people watching you, think of it as you riding your horse. Trust yourself and trust your horse.
Balance or Serenity blend essential oils. And it took me 20+ years to grasp this...go in like youre schooling. Not laid back, but just with the mentality that theres no crowd, etc, youre just on a nice easy hack, and its just you and your bud
And trust the horse to know what hes doing. They feed off of your nerves big time, so if youre nervous, they will be because you are