My story is not a whole lot different than many of those above.
My dad had a couple horses as I grew up. Mainly we used them for hunting season, a few rides during the year. As a teenager my interest moved more to objects with motors and faster speeds.
In 1983 the Forest Service closed off a lot of area that we used to hunt to wheeled vehicles. The only way into where we used to hunt was a long hike or horses. I went a few hunts with friends on their horses, a few pack trip in fishing. About 20 years ago, the opportunity came for me to own a horse and I jumped on that opportunity and very quickly realized I knew nothing about riding or caring for horses.
Over the last twenty years, I've owned about 20 horses. Had 3 foals that I've raised and that are now are my main trail riding horses. I have broke every horse that I've owned. Too cheap to pay for a already trained horse. My first horse was a 3 year old Arab/Saddlebred and a true handfull. I'm lucky I survived teaching myself and a young horse. I don't reccommend the Green on Green approach.
I read books and watched videos. But I think the best thing I ever did was start going to NATRC competitive trail rides. At these events, I had a horsemanship judge and a vet looking at me and my horse several times a day. I learned how to spot when my horse was sore, to understand his hydration, respiration and heart rates. How to camp and care for my horse. Often the judges would ask me to handle some obsticle and my answer was often, I don't know if I can do it, But if we fail today, I will be able to do that at the next trail ride. It would give me something to go home and practice. We didn't win anything the first year. But both my horse and I learned a huge amount.
After 6 years of competiting and having judges dock me for small things. I gave up the sport. I'm happy now days to just get out and enjoy a good trail. To see new country. To enjoy an afternoon with my daughters or friends, To spend some time with the horses.
I never took any lesson. I'm basically self taught with the help of watching friends, other horse people and the comments from judges at the competitive trail rides I attended. I'll never compete in dressage or western pleasure. I doubt I ever attend a horse show. But some how, I've started and trained 20 horses over the years. People are impressed with my horses and buy my older horses as I start working another youngster. My wife daughters and my daughters friends all ride my horses and feel safe. So I've done something right. ( But I have made lots of mistakes along the way).
My advice is read some books, watch some videos and get on the horse and go enjoy. I'm 60 now and hope I'm still enjoying my horses at 80. My dad is 84 and hasn't ridden for a 30 or more years. He has been bugging me to let him ride one of my horses. So I finally gave in and put him on one of my mares for a ride.