Ferretman: First! WELCOME TO CoTH! One thing you will get here (as I’m sure you’ve already seen) is unvarnished opinion from all comers. Most of it knowledgeable and well informed about horses, and the myriad of issues surrounding them.
Now. When I started taking lessons, I was also taking weekly 1 hour lessons. It took me much longer than 4 months to develop my seat to the point that my instructor was willing to let me try a canter. It was closer to a year. Your instructor should be thoroughly grounding you in the fundamentals, and be sure that you are secure and doing well at one gait, before asking you to go to the next level up. Your trot should be light and well controlled, with your seat, legs and hands staying in place and going where they need to be to communicate with the horse. Unless you’re at the track, riding isn’t about speed. It’s finesse.
It sounds to me like you have been rushed a bit.
That concerns me.
How did you find this trainer? What are her credentials? How much shopping did you do?
About size: Personally, I don’t worry about how big the horse is, except when trying to mount from the ground, or falling, and I’m a 60 year old lady. Every horse in the world is stronger than me. They’re stronger than you too. But as you are a 6’ guy, I can see why they were putting you on a larger mount, but still, there are plenty of horses out there that can carry you just fine. (like others have said)
This guy just wasn’t the right one for you—a pretty much rank beginner.
Are larger more difficult than smaller? They are all individuals, but ponies have a bit of a rep.
http://www.richardbealblog.com/wp-content/uploads/2012/12/santa.jpg
All horses have good and bad days, just like people. A horse who has a few small spook issues on a good day will be that much more so on a bad.
If you are good with your trainer and want to stay with her, go ahead and see what other mounts she has to offer you. Part of learning to ride, is learning to ride different horses. They are all individuals with their own ways and quirks. Riding different horses will also help you find the personality of horse you mesh with.
And when your trainer says: “What do you want to do?” You answer with: “I want to ride a horse. I want to be GOOD at it. And I want to have all my fundamentals in place. At this point in my experience with horses, I’m not sure what direction my path will take, but whatever it is, I’ll need to start from a solid, well-laid foundation. Give me that.”
Don’t get discouraged. The good part of horses can be found in a thread on here:
http://www.chronofhorse.com/forum/showthread.php?422004-What-special-times-have-you-had-with-horses-that-stand-out-in-your-memory
So you see, it’s not all about riding a bolting guy that doesn’t want to behave. Once you get into it, and you have a few nice experiences of your own, I think you’ll be hooked. Welcome to HORSES!