Others have said it... But it works... Go easy and just take things as they come... I went through something similar, and am now doing the same on the ground after having a boarder kick me (broke my wrist in two places, could have been worse, but it really rattled me for some reason.... Everytime I work with a horse I give myself a pep talk about how there is no point worrying about stuff because I will only manifest my fear in the horse!)
My "excuse" for being fearful was that every time I get hurt (regardless of how I did it) it is a MAJOR pain in the ass. It was making me unhappy to be using such an excuse though... Seemed wrong that I should let something silly like fear of doing something I have done most of my life take away from something I enjoy.
The first real "test" for me was getting up on my big Clyde mare for the first time in her life. I don't know how long she and I were "working" on the ground that day, but I had dragged a big garbage can out and was determined to get as far as having her Ok with someone above her.... Over the next few minutes I found myself hanging over her back with her looking at me like she was saying "Really? That the best you got?", I stood up again and told myself to pony up and swing a leg over... And did it. Sat up there clinging to her mane, eyes shut, waiting for the freak out, and.... Nothing. Opened my eyes and saw her looking back at me again "Was that so hard?" complete with a little head nod. It didn't seem SO bad, so I sat up a bit taller to signify I'd like to walk.... Walk we did, at the end of it all I felt about 10 feet tall (and that was AFTER I got off
This is us that day...
I won't say it was entirely that easy, I still have bouts of this new and frustrating fear (after 20 years of riding!) but still take the same route... Once I am comfortable it seems easy, even it means it takes me awhile to summon the courage... It always seems comical in hindsight, but there is nothing funny about fear.
I find the trick is to identify the fear, then push it away... Different people have different approaches, I focus on it and then think of myself breathing it away on deep breaths.