A couple of shooting specific exercises that help, in addition to the normal ones, are:
Hand strengthening ones using a soft squeezer ball.
Wrist strengthening ones winding and unwinding a light weight attached to a rod and string.
Pushing a weight out from chest height, holding it a few beats and pulling it back without letting it dip down.
It's never to late to start.
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”