I can really identify with the first half of what you described. Thankfully, I haven't had prostate problems, but my father has been treaded for prostate cancer and dealt with the some serious side effects, so I'm aware of the frustrations you might be experiencing.
To comment on your other observations about getting older, I've struggled a bit with the same things. Maybe it was all in my mind, but there's a certain confidence, a swagger, that comes from being a young buck. Whether fact or fiction, I always had the feeling that I could "take" any woman and show her a time she'd never forget. I didn't think my work was done until she'd had several orgasms. And it didn't matter where we were, if she showed interest, I was ready, willing and able.
But now, I've lost the confidence that came from my physical abilities and it's taken me a while to reassess my role as a man and the way I relate to women. That sentence has been a big one for me in the last few years and I didn't see any women for a long time as I was adapting to my new reality.
I now worry about what happens if and when we get intimate, and will I be able to perform? What if I've had a few drinks, what if the hot tub made my cock and balls go limp- I now have to think about situations and preparations that were unheard of 20 years ago. It's just a different world when we age.
But even though it's changed, the desire is still there and so is the payoff. As I've posted previously, spending time with an attractive woman is its own reward, and it's always time well spent even if you aren't able to effortlessly give her multiple orgasms like you did in the past.
Maybe you'd call it part of aging gracefully, but I've now accepted the fact that I am what I am, and have the confidence to let women either accept that or not. I won't kid you, I spend a lot more time alone than I did just 10 years ago, but I'm OK with that and it doesn't weigh on my mind like it did a few years ago as I noticed my sexual prowess declining.
I used to be a stud, now I'm not. I used to hang my bath towel on my erect penis while I shaved. I don't even know why it was always erect, but it was. Now, I can barely get it to salute even when I want it to. There's nothing I can do about it, so I enjoy the company of women in the ways that are still available to me, and it's all good.
I'm still filled with the same sense of expectation when a woman smiles at me as I did when I was 18. And it's still as exciting to unhook a bra as it was when I was 21, and women are still as soft and warm as they were when I was 25. And they smell just as good as they did when I was 30, and they taste just as good as when I was 40.
So there's still plenty to enjoy, it just takes a while for your mind to adapt because I think our sexual self-image is formed when we're young and discovering sex in general. But all of us on this board are old enough to know that life is about change and the better we deal with it, the happier we'll be.