Hi Nigel,
OK - You need to deal with two simultaneous developments, firstly you are 60 and growing older, so you will anyway be losing physical prowess, strength and stamina are ebbing away, and staying awake all afternoon is increasingly difficult.
Against that background which applies to all healthy 60 year olds you have the added bonus of prostate cancer and you are on hormone treatment.
First time around I was on hormone treatment for 3 years and like many I was concerned with all of the 'here and now' side effects, like hot flushes, the hairs on my legs etc. What I didn't notice was the slow, steady, remorseless loss of muscle, the loss of strength, the fact that after 3 years without testosterone I had the body of a 57 year old boy.
I then had two, nearly three years off the hormone treatment, and without really trying I found that my muscles, strength and stamina started to improve, I started to get back the body of a man.
So do not despair, if you accept the first premise, that due to normal healthy ageing, you are never going to be as fit as you once were, there is every chance, that without really trying, once you stop the hormone treatment you will definately improve on where you are now.
If you follow the advice of some blokes on this site and join a gym and/or take up swiming, running, walking, weights, indeed anything physical to coincide with the end of your hormone treatment, you might do even better?
All of the above is of course working on the premise, from your profile, that in a year / 18 months you will finish hormone treatment, and I hope it works out for you.
However for guys who are on hormone treatment longterm, or guys like me, who find themselves back on HT, there is always the intermittent approach. I don't know enough about that to offer any advice, but if you check out George Hardy's posts you will find lots of sound advice on intermittent HT.
Best of luck
:)
Dave