Start practicing what you're preaching because, once again, you're going down the same road. Re-read the first page of this topic. Yes there were a few people who held your past against you (can't blame them), but you also received solid, reputable, realistic advice from others. If you were taught to walk away from/ignore something you don't want to hear DO IT.
Believe me, I know what it is like to be a teenager with champagne goals and a beer budget (or, in my case, more like a Boone's Farm budget ). I am not much older than you now, in my early 20s, and I can still vividly remember the physical pain I felt over not being able to show as much or afford as much as the girls I rode with. I also had lofty dreams of being able to find a catch ride on a 3'6" horse because I deserved it so much more than those other girls. But why - because I struggled? Because I spent hours every Saturday working in the barn? I eventually learned that none of the mattered in the Big EQ ring or the Junior Hunter ring. And eventually I learned that just because I couldn't show at WEF every winter or ride with Andre didn't mean that I couldn't love and enjoy horses. So instead of whining on COTH or yelling at "these people" (god I hate the term "you people") I went to the barn. I played the ponies I did get to ride who were not 6 figure horses by any means, but had a lot to teach me in their own right. I fed alongside my trainer. I cleaned tack right next to the girls who DID get to go to Florida every year and I found out they had problems and struggles of their own and we became situational friends. I watched my trainer ride and learned a lot. I went to endless horse shows and a lot of times I didn't ride for the entire weekend, but I cheered on my friends and I got to watch a ton of really really good riders ride. And I learned the ins and outs of the show world (which makes me a very valuable member of the barn now). And sometimes I did get to ride - sometimes it was the crappiest, ugliest horse with the meanest stop and sometimes it was a nice sales horse, but either way I was honored and ECSTATIC to have the ride. Because believe me you, no matter how crappy the horse is and how much of a "favor" you think you're doing for the owner, there's another kid out there who wants the ride just as bad and will do it with a better attitude. So I always said thank you and I never blamed ugly crap-head (terms of endearment, I swear) for our mistakes in the ring.
And now I'm a 20-something and guess what? I never did make it to the Big EQ ring. But if I had, I would have probably made a fool of myself anyway. No I wouldn't have fallen off and yes I probably could have piloted the course, but no where near as well as those girls who I used to say "didn't deserve it like I did". I still don't have a 3'6 horse - in fact I don't have any horse now because boyfriends and college and dogs and trying to eat something other than pop tarts now and then has gotten in the way. But I still have a good attitude and I still sit on anything with a smile on my face and I get rides. Usually not the best ones, but sometimes I do get to sit on a really nice horse and either way I ALWAYS hand back the reins with a huge, genuine "thank you".
So yeah, realizing that you're not going to accomplish your initial goals sucks. It's hard. And it hurts. And sometimes you want to give up. But not giving up marks the difference between the people who will accomplish SOMETHING and the ones who will accomplish nada. And that's why they say you should shoot for the moon - if you don't make it, you'll land among the stars. What the heck is wrong with a 3' goal for now? The 3'6" divisions don't disappear when you turn 18. You have your whole life to make a lot of money and buy nice horses and jump big fences and show against the best of the best. So for now, suck it up and realize that these big mean people of COTH aren't being mean for the sake of killing a kid's dreams. They're being realistic because they have been there and they have accomplished goals and they KNOW what it takes.
And the thing that will set you apart in the horse world (other than money) is attitude. And frankly my dear, yours sucks. So revamp or expect a lot of disappointment to come.