(I hope it’s ok that I answered instead!)I find that just focusing on breathing really helps me. Also to reapeat what I am doing wrong, or chant it out loud in a rhythm that matches my breathing pattern. Finally another good thing you can do is ride bareback and just walk around letting your horse wander and you trust them.
If you get nervous when jumping count a rhythm like 1...2....3 etc. Or focus on your striding.
Hope this helps!!!