I have a 9yo OTTB who sounds similar in ways. Pippa is a doll on the ground, loves to jump and is very willing, but she has a tendency to be ‘up’ – very up, sometimes! Things we do:
* Earplugs – they definitely help her focus. She (at least appears) to like them – she puts her head down for me to put them in.
* Regular riding – and by regular, I mean every day, if possible! Generally we jump her two or three times a week, with ‘hack’ rides in between (these could be almost anything – w/t/c around the ring a few times in each direction, flat exercises, a trail ride, whatever). The more we ride her, the better she does.
* Exercises at the walk. Not very exciting, I know… but sometimes I’ll let the reins out to the buckle and work on guiding her just with my legs at the walk – circles, figure 8’s, serpentines – the goal being to get her to relax and learn that she doesn’t have to be ‘up’ when she has a person on her back.
* In lieu of lunging, just cantering around the ring for an extended period of time to take the edge off, so to speak (2 min in each direction, repeat as needed).
One thing we definitely try to do is reward her for relaxing. She’s the sort of horse who will pull back if you just haul on the reins, but she responds very well to half halts and sea-sawing the reins lightly. If she gets real strong I’ll give one pull and then relax the reins immediately if she slows down.