My current horse is literally an OTTB. I bought him off the back stretch, cash on the barrel. As noted previously, these horses are unbelievably well trained in many ways.
I’m not sure if you have this or you have a horse that went through some form of retraining or other and is more of an “indirect” OTTB. You don’t say if you are doing your own training or working with a trainer.
I am FOUR YEARS out and we are still slowly growing and learning. There is NO timeline nor any explicit determination for training. I would say my guy is pretty much a completed Novice Level Eventer/1 meter jumper/1st level dressage horse. But in my mind, because of my background, he is still green and growing. His next phase of training is lots of competitions. I look at a 5 year plan of training rather than months or even a year.
1 step forward and 5 steps back always happens. It is the good trainer/rider/horseman who recognizes this and rephrases the training to set up the next 7 steps forward and patiently works these steps as long as it takes.
Other issues are that as green horses learn their ride changes! You don’t ride an unbacked horse the same way you ride a 1.4 meter jumper or a grade stakes racer. You have to be able to change your ride as the horse grows so you ride less defensive and work more to a dynamic ride. Sometimes this change happens in a week and sometimes a year. The key is to make sure you aren’t riding the horse you had yesterday. You have to ride the horse you have today and tomorrow. Ride what you have at that moment but also ride expecting the horse to grow to the next level. The horse will tell you if they are capable.
The zero brain cells are AWESOME!! The genetics of an OTTB tells them to RUN. You can’t fight that and nor should you, in my opinion. The key is to make sure you have enough road and runout that they can do it. It is something that is almost impossible to answer in an arena. Of course you, as the rider must be confident and competent so that you can let them run out under you. There is an insane amount of joy when they truly pull onto the bit and go into a real, full out gallop, with a genuine suspension phase in gait. There is almost nothing like taking a full cross and dropping down, letting them answer what their heart tells them to do. It is the closest I’ve ever come to truly understanding a horse in their language. So, yeah, I will never try to eliminate the “green” zero brain cells moments. Their brain is functioning fine. They are just chasing their hearts.