Affiliate Marketing Secrets

I have a 19 year old TWH gelding that I have had for 14 years. In all my years owning him, we have really found his “niche”. He’s done just about everything and I was riding him consistently until about a year ago. He was fed up with endless circles in the arena and just wanted to rush through everything(including trail rides). I ruined his work ethic and he was disconnected from me. So I gave him what he deserved, early retirement. He has been out at pasture(not counting occasional rides this summer) for the past year or so. I honestly haven’t been giving him the attention he deserves, but he isn’t lacking. I went to visit him today and he seems like he wants to re-connect. The thing is, I don’t know if he’s too old to re-train. I want to ride him again, but the reason I retired him is because no matter what you did, he wouldn’t slow down, he was go go go all the time because he just wanted to get it over with. I can’t work him in a pasture or arena without him acting like this and I wouldn’t immediately take him on trail after a year off of work. He would be sooo full of it and go so fast. I was thinking about possibly cart training him. When he was recovering from an abscess, I spent several hours ground-driving him to work him back up to being ridden. So he has some experience and did well.
I want to know if he is too old to re-train and if he isn’t how should I go about either(riding or cart training)?
He is sound and has only had a few soundness issues over the 14 years I’ve owned him. He had an abscess last winter, a minor stone bruise in the summer 2009, and was kicked in the fall 2006. The last couple years I rode him, he had sporadic mystery lameness in his left leg that seemed serious because of his TWH head bob, but the vet said it wasn’t, even though he couldn’t figure it out. We put him on regular cosequin and it cleared up. He hasn’t been on any supplements in over a year and is sound.
What do you think…
Thanks!