I'm not sure how I found this forum, but I'm glad I did. Y'all have a lot of encouraging suggestions and advice.
I'm dealing with the same issue. After over 25 years, I decided to re-enter the horse world. I, too, had a bad fall. When I was 13, I was thrown from my favorite school horse into the cinder block wall of an indoor arena. I knocked out my front teeth, broke both arms, and severly bruised my left knee. It was months before I was back in the saddle again, but from then on, fear aboard a horse was my constant companion.
As with many folks, horses were put on the back burner while I went to college, got married, had a son, moved from NY to NM, went to grad school, got divorced, son starts school, is diagnosed with Asperger's Syndrome, I quit grad school, get a full-time job, buy a house, get a dog, get another dog, buy another house, get married, buy another house...
So now my son is in college and it occured to me that there is room in my life for horses again. I immediately re-engaged in my former obsession. I visited every Rock Mountain Horse website I could find after learning about their loyal, low-key personalities, smooth gaits, and smallish size. Of course now I want one. But, I also want to be able to ride it.
So last Sunday, 25+ years since my last ride, I was in the saddle at one of the few local stables that teach English. I was shaking because I was so excited and proud of myself when I found I could still mount a steed directly from the ground!! I adjusted the stirrups, urged "Foxy Roxy" forward and found myself in complete control. My form felt good, lower back relaxed -- Roxy responded well to my signals. It was Nirvana!! For about, I'd say, maybe 5 minutes. At which point all of my riding muscles melted like room-temperature jello. At that point all I could do was flounce around in holy terror. Fortunately, the riding instructor is very understanding, patient, and supportive.
I've spent the past week googling "exercises for horseback riders" and found some useful tips. I do them all day at work. I get a lot of funny looks but I don't care.
So that's where I'm at now. Tomorrow we'll have lesson number 2. I'm excited and nervous, but mostly I'm so happy to find others who are and have gone through it. Thanks, everybody!