Since I ain’t got the money nor the chance to by my own horse I’ve been used to ride on of the stable horses to learn all the basics. But here’s where thing go wrong (at least for me), for a long time now I’ve been doing the basics pretty well, my confidence was up and the horse I was working with was really helping me.
I too ride RS or stable horses and I dont want to upset you but I hope it may help if I look at what you wrote. It sounds as if your lessons have become boring? And you need to ask your RI if you can introduce some new things perhaps? I used to ask our RI to set me a challenge to ask me to do something she felt I would be unable to do and then (when I failed) we corrected it and tried again till I managed.
Then I wonder what you mean by basics? Basics themselves are pretty complicated. Do you mean being able to ride walk, trot and canter and halt and back up in the school?
Do you mean being able to change between those gaits (transition) when going large and on a circle in both directions?
Do you mean direct transitions (changing to the next gait like trot to canter) or indirect transitions like Halt to trot or walk to canter. Can you practise transitions on a circle? (I am not good at circles) Can you go large alternating 5 steps walk and 5 steps trot? Or the same, riding transitions from trot or walk to canter?
Even if you can do all these, I should warn you that it is a different matter if one tries to fit the pieces together and to ride even the simplest dressage test. This is how I got it less boring.
One winter when the weather was not good for hacking, I had a weekly private dressage lesson on a beginners' pony. I bought a set of tests, and printed one out to take each week. We started with the very simplest test and due to my age and to avoid stress we paused the test now and then, so I was accomplishing the test piece by piece without my running out of breath.
By the end of the winter we had worked through the movements required in many tests and I had got to the point of learning a flying change. We did this because I had talked to the teacher. If there is something you would like to learn, or something you aim to ride, you must tell your teacher or they will not know.
You say the horse was helping you. I wonder who told you this and what does it mean? Horses dont reallty help people. They may keep their attention on their rider rather than look at other things that are going on. They may copy the horse ahead of them. Many of us learn to canter by following the teacher. But that is about it. Is your teacher implying that you are giving the wrong cues and the horse is ignoring you? If so, she needs to teach you how to do cue it right.
What I was taught was that we help the horse. We get the horse in a position where it is able to do what we are going to ask for next and then we ask. The preparation is as important as the actual transition.
When you say you are not confident, really none of us can be confident a dressage test will go right. It doesnt matter if it goes wrong, You can try again.
But if you mean safety, that you are scared of falling off, or that your horse may spook, that is a reasonable fear and you need to talk to your instructor and take things very slowly. Do a whole lesson in walk if you need and get to feel safe on a horse again. My rule if I dont feel safe on a horse is to dismount and ask for another.
To cheer you up - I still ride what you call stable horses. I have ridden three or four of them long term, and you are right that it is a real pleasure to be on a horse that one knows well. However, I was like you, I went to Riding schools and hacking centres to learn to ride, and I rode many different horses. And that was all part of my riding education. I never looked like an advanced rider, nor passed exams, my progress was invisible. But over the years I became someone who knew how to ride.