Right now I'm jumping 18" verticals and x-rails. Occasionally doing up to 21" (about the same difference as an 18", really). I'm new to jumping, but I've been riding 12 years, did dressage for the most recent few.
Right now it seems the major issues I'm having is me snapping up too fast after I land. I did have one bad lesson where I was getting left behind, and almost came off a couple of times. Amber refused a fence for the first time ever (it was ENTIRELY my fault!). It was just a weird/bad day for us. We came back strong yesterday and my trainer thought we looked pretty good. She said our approach and take off was great, but she said the big thing is I'm snapping up too fast during the recovery. I tried it a few more times trying to stay out of the saddle a little longer but she said I was still coming back a little too fast.
I wish I had a video. I know it would be helpful, but I was still wondering if anyone could possibly give me some ideas on why I do this and how I could fix it?