Ehh, I think sometimes you have to take what doctors say with a grain of salt. My doctor recently told me to sell my horses and rent a trail horse occasionally because of my Crohns disease. No way, no how. I own two currently, and plan on adding a third at some point.
My boyfriend has some serious ADD, but he's still in the barn with me every day, for a minumum of 2-3 hours each day. He rides, he cleans his mares stall, he feeds his mare, and he fixes things around the barn. He gets done what needs done.
Of course, he will leave a stall open now and again, but thankfully someone is almost always around and his mare is good about that and never tries to escape lol. My pony on the other hand will take any excuse to leave ...she doesn't go far though
I would definitely agree with keeping a check list - I myself need to do this as I am just super scatter brained. I'm not really ADD, I just have TONS on my mind and get bored easy so need to constantly be doing something which then = forgetting everything else in my head.