[QUOTE=Wish_Upon_a_Star2000;7961215]
All my friends horses are easy-going,and yet I feel uncomfortable on any horse that isnt mine!I feel uncomfortable and not-so-confident on any one else’s horses…!!Does anyone have any advice to help me with that??[/QUOTE]
The only advice I have for you is to become a better rider. The more confident you are in your riding ability, the more confident you’re going to feel when you get on strange horses. If I’ve understood you correctly, you do have another horse that you can ride while your new horse is recovering, so get out there and ride her. Ride her as often and in as many ways as you can. Ride every day, even if you’ve only got time for 15 minutes in the saddle or a 5 minute bareback ride around the pen. Ride.
You say lessons are out. OK, fine, then get some good books. Get some good magazines. Study the pictures. Get someone to video you while riding. Everybody has a cell phone that takes videos these days. Watch the video. Compare what you see with the book and magazine pictures and videos of good riders you can find online. How do you compare? What are you doing differently? What do you need to do to look more like those pictures and videos?
Editing to add:
I’m going to, well, not disagree with the standard COTH wisdom, but offer an alternative viewpoint. The best way to learn to ride is by taking lessons. The only way to become a polished rider with good technique is to take lessons. Everyone who wants to ride seriously ought to take riding lessons.
However, a lot of people grew up riding wild ponies and old horses in the pasture with little opportunity to take riding lessons. I was lucky enough to have parents that could afford riding lessons. But I rode at home with lots of kids who had no interest in formal lessons or the ability to get them even if they were interested. Were they pretty riders? No. Could I have kicked their butts in a show ring? Sure, five ways from Sunday.
But did we all ride wild through the countryside together? You betcha. Did they mistreat or cause physical harm to their ponies or themselves in the process? No, no more than I did.
I was in 4-H with a young man whose parents were kind of like the OP’s. They bought him a horse, for Pete’s sake, what more did he want? But, he was really serious about learning to ride well. He was like a sponge, soaking up information and never missed an opportunity to participate in 4-H clinics and work days. He remained a little rough around the edges (wouldn’t have won an equitation class on his best day), but he was a lovely, soft rider and his horse was just a gem (my first ever extended trot was on his horse).
no doubt about that!! and maybe it was caused by a poorfitted saddle.but another reason that fistulas form is if they are ridden long and hard and/or suddenly ridden out of the blue for a longer time…which would more have likely been the case,as the trainer wasnt able to ride her much during the summer,then probably started riding her once she decided to sell her…and I’m not pinning the blame on anyone tho.Its not my place. 
the vet did say that it could’ve been as simple as rolling on a rock,or getting kicked when they were establishing the pecking order.
i never had a fistulous horse before,guess thats why I dont want to hurt her???