Bud, I'm currently 55 years old. I've had MS since I was 40 and had to quit work when I was 49. I can't tolerate heat when it goes above the mid 70's....so when that happens I just don't go out doors. In the summer, when I go out...it's when the sun comes up but I'm back home by 9:00am.
I will do my reloading in my garage as I have a window A\C unit. Without that....I could not be out there. I try to hunt and shoot year round. I get around in the woods with a highly modified electric EZ-GO golf cart. Without that, my hunting would be limited to 100 yards from where I park my truck. With the buggy....my hunting world has opened up a bunch, and my freedom to go to a shooting range and hang my own targets and take 'em down has made a huge difference.
You can't be concerned with what you can't do. All you can do is focus on what you CAN do. Then just go out there and do it on the days that you have the energy and ability to do it.
Dave