You can do this, there are many of us addicts, older, frailer, fatter more sensible than our skinny "old selves"
Don't compare yourself to the person you once where, start with a clean sheet now, now expectations of yourself, just to enjoy horses.
I started just working on ground work and grooming, just enjoying my horses, and built on that a small step at a time, how small
1) wear riding clothes around the house and in the barn, start to feel like a rider.
2) as part of ground work get the horse used to a mounting block, you are NOT going to be riding, just getting a horse stood next to the block, leaning over etc etc.
3) when all of that becomes fun and stress free then mount, dismount, enjoy
4) Mount small walk dismount enjoy'.
It is by such small steps that I get myself back in the saddle every time I have a wobbly, sometimes it takes a while, sometimes I can breeze through it all in a day or two