Cherie said it well.
So I will just add some suggestions
- a few lessons with a GOOD instructor who can help you stop nagging, and start requiring instant responses will help.
- he needs to be fit, and to fittened properly. This is a big subject, so I will confine it to advice to work on his fitness so that as you ask for more, he has the strength to give it without injury.
- do you have any hacking routes with some good gallops on them? If you can, start to up the speed of your hacks and get him used to some good all-out gallops. He needs to be fit first though! Go in company at first when you can, he will be happier to go go go with others and will really only be happy to go on his own when he is super fit.
Are you in hunting country? If so, make Autumn Hunting your goal and if you enjoy this you can transition to full hunting. There is nothing that livens a horse up better than hunting.
Get up, get going, seize the day. Enjoy the sunshine, the rain, cloudy days, snowstorms, and thunder. Getting on your horse is always worth the effort.