You'll laugh at this - I hated turning 20!!! I suddenly realised my mortality at that age. I am going to be 56 tomorrow, it's not so bad. TBH, I find there are compensations for getting older - ok the menopause sucks donkey balls, but there is the whole "when I am an old woman I am going to wear purple" thing kicking off.
I find I care much less of what people think of me as I get older - I am what I am - take it or leave it. I don't think there is any reason to be less desirable over 50 - it is down to the twinkle in the eye, that is what the opposite sex find attractive, they don't notice the saggy bits etc - especially as they have got the same, unless you are a cougar out for 30 year olds!