Until I was 80, I was managing quite well. Since that birthday 4 1/2 years ago have definitely started to fell 'old'. This was made even worse by my constant tiredness, falling asleep all the time, no matter where I was. That has now been sorted out and my use of a CPAP machine each night has given me back my daytimes.
Have very little mobility - thanks to mobility scooter I am able to get out and about to meetings. Try have to something to work each day around.
Fortunately, I feel quite 'young' mentally. Even my children (in their fifties) say I seem to remember things better than them (although this is probably because I have a much more stress-free lifet=style than them). But I do find that by the early evening every movement is difficult for me. So, I get into my nightclothes very early, and do manage to do my knitting whilst watching tv.
My great fear is losing my eyesight. As long as I have that, I can continue my independent living - and this is very important to me.
So, yes, physically I feel my age, mentally I do not.