Do the unexpected! He'll be expecting to work and be drilled. So just have fun, maybe jump on bareback and hack around. Or go on a beautiful trail ride. Something besides Walk-trot-canter-stop-turn-reverse.
Let him think that being with you is FUN and that he want's to be with you because you aren't going to drill him like a lesson horse.
After he has a better attitude start from the begining and reteach him those wonderful manners, but you want him to be happy first then this part will come a lot easier
Hopefully that was the kind of answer you were looking for. If not just holler!