I had the same issue, and we all do! At some point... I just learned to focus on the course and my horse. It’s just like practice, they all say, but it is... I literally got to a point where everytime I go in I cancel all noises and people and everything and all I see is the jump and my horse. It takes awhile but everytime you go in just don’t focus on the people look at whatever you’re going to and do it like in practice!
There’s a really useful book called “transform pressure to power” by Helen Rennie. Genius!
I get super nervous too and often have panic attacks, I really find music helps when either tacking up, warming up or just relaxing before a class x
Keep remembering to breathe! If you can’t, try talking to your horse which will help calm you and force you to breathe. Sometimes I sing a song in my head and ride to it. Hope this helps!
I just try to remember that I'm there to have fun and that I shouldn't be riding for anyone but myself. If I go in the ring focusing on having my best round possible not what would be necessarily the "winning round" it calms me down a lot