Mantra, no o in the word.
Good advice has been given here on this. And there was no need for you to not be gracious whether or not you agreed with it.
Have you looked to see if there is anything out there that deals with the arthritis issues you are having in terms of driving? Maybe something to limber your fingers, or to make reins easier to hold onto. The reins recommended may do the trick, and also wonder if the area where you normally hold could be made slightly more "tacky" so as to afford a better grip?
Are there any exercises that might help with the mobility of your fingers and hands?
Horses make me a better person.