All of us over 50 have been there and many people under 50 have already faced this, and that's the reality we can't be and won't be who we were, healthy and fit, ready to do anything we're physically capable. The mental health changes when we discover our bodies don't work as well anymore and won't do what we did before.
Nothing new or news there, just the reality of getting older, and for many, getting sick or injured for life. This recent bout of problems (digestive system infection, or some professionals think but not the specialists) caused me to stop running and hiking. The better, or is it the worse, part of two years I won't get back. I miss running and while I can resume running, it will be with a different perspective.
I now know why I run out of breath quickly past any point of physical exertion. I can recover to some degree, but the body just can't do what it did. And although this problem is nearly 20 years old, I just slowed down or walked until I could breath again and continued running. I kinda' knew this when the walks were longer, I just ignored the reality. Now I know the reality.
So I've gone back to walking, 5-6 miles for starts to the local commercial center near where I live. It has a lot of places including several cafes to get a reward of a coffee drink before buying carryable stuff and walking back. Once I get my legs back under me I'll resume the weight training which I stopped because first I realized I reached my maximum muscle development and second the problems made me too tired to even try.
I read where we're born with the genes which controls our muscles more than previously thought. That's common sense, but having almost all slow-twitch muscles, not the fast-twitch muscles necessary to develop muscles, I read that our genes also determine the maximum muscle we can develop (meaning more strength training doesn't produce more muscle, just more exercise), I simply couldn't get stronger and won't get stronger than I was. I can get back there to some degree, just not any better.
And that's my lot in life now past 60. Not fun but I can't complain. I do and will still complain but it's really meaningless and useless except to waste energy. But now I can simply walk it off while my physician and the specialist argue about the cause of the problems and find a treatment, if one exists. It's the old adage, "It sucks getting old."