Cortrasna - If you are able to ride and do ride, that is the best possible tonic and health benefit even if you just potter about.
As for Ground Work - RS riders dont do any, not with capital letters, unless they pay for a lesson! None the less, we do it all the time and so do you - fetching a horse, tacking, untacking and grooming which I imagine you do, is all ground work. If Dolly has a stable, going in and out of the stable and how she behave when you enter is ground work too. Often called, Good manners.
I am struggling with weight at the moment -I've only gained a pound or two but I know riding is harder for the horses and falling is harder for me, if I am heavier. So it is a bit of an incentive. At least you have a horse - Our RS ius now closed 2 days a week and I havent been able to fit in rides between other things in the diary. It has been down to once a week.
Enjoy your summer and forget the rest.