You don't feel old? How about if I told you that a child born when you turned 18 is now a sophomore in college. If you had a kid when you were 18, he'd be 19 now. Or if you knew any girl in high school who had a kid, that kid would be in his 20s right now. Feel old yet?
> However, increasingly, I see I’m not as fit as I once was. This is the inevitable process of ageing,
As my grandpa said, aging is a slow decay. You are slowly rotting and you and your clothes will get that unmistakable old people smell.
> Again, I feel young, in the sense that I’m still impetuous about my career and still have aspirations of doing something I enjoy, rather than something that pays the bills.
It's like that cat stevens song says "For you will still be here tomorrow, but your dreams may not".
That is getting old.