Our pony was getting naughty because he worked out that my 9yo would get scared and he'd get out of work for the day. Her confidence wasn't the greatest to start with and he made it worse. She's pretty much given up riding now. But the positive thing was getting my confident 10yo on him to sort him out. She just rides him through everything he throws at her until he gives up. It is great to watch and now he's finally worked out that playing up means extra work! We now have a pony who behaves most of the time and my 10yo really enjoys riding him. The 9yo may go back to riding one day but right now she's happy to just groom and hang out with the ponies.