I never remember ever being nervous or uneasy around horses up until a few years ago.
I've always be alert to what could happen, when you work with horses pretty much daily? You just expect things, but aren't nervous per se.
But after getting caught in trailer with a fool on outside with rubber tie stretched to GA and back??? And the subsequent mobility problems I am having? I am more aware now at 57 that I cannot move fast enough to get out of the way in emergency, nor am I able to get in and out of trailer easily now.
To me, the best way is for you to groom many horses, lead them, move them around, and in general get so familiar with them, the nervousness fades. That is the only way you will get over this.
Every time you can pick a strange horse's hooves up, move it over with voice or body language, or lead a horse and give it the eye that says you had better behave?
You will gain confidence.