Do you drive yet? Flat classes are very much like driving in heavy traffic. You constantly check everything around you, know where all the cars around you are and “ drive ahead of yourself”. Anticipate whats coming up- is your exit coming up and you will need to change lanes? Traffic merging with you? That stop light ahead turning yellow? This gets easier the more you drive but when you are a new driver, it can be overwhelming.
Like driving, riding in a crowded flat class means you need to be alert and aware of everything and everybody. You want to maintain the same speed as the majority of others in the class and, NO, you don’t want to make “ awkward turns” because if you do, you will cut off somebody else.
Going to get on you a little bit here…you are new to the sport and young. Take this as a lesson in how many hours of practice its going to take and how many shows you will need to go to if you really want to get good at it. IEA is more complicated because nobody is on a horse they know well, its the same for everybody but its never as smooth as a big flat class where everybody is on their own horse and can predict exactly how that horse is going to go. Catch rides are crap shoots, you need to do the best you can with the horse you have. Its very, very hard but will eventually make you a more thoughtful rider.
Go to more shows, go in more flat classes.
Except for Show Jumping, this is a subjectively judged sport. Its a judges opinion. The judge here pinned you 4th because they thought 3 other riders were better. Ask your trainer what it was the riders did better then you? Better leg? Quieter hands? Better transitions? Did you, maybe, look down causing your shoulders to slump?
Or were you just not as experienced and so not as polished as they were? And, as noted, they may have handled the class traffic better because they have more experience doing it? Does your trainer have any thoughts?
Really, trust us here, you WILL get better if you stick with it and go to more shows to get polished. Also. 4th at Regionals is nothing to be ashamed of, any ribbon at a higher level then you have been doing is a win for you. How many were in the class?