Hm-m-m-m... well... I sort-of remember what 60 was like I guess.
No, I've never thought too much about particular age milestones. I've not been especially fond of the aging process in general though. Plus I don't tend to be conscious of the fact that I'm as old as I am. In fact I often have to remind myself that, hey... you're 70 years old!
Anyway I guess "you're only as old as you feel" as the saying goes. Or perhaps... "age is just a number".
And then there's "if you don't mind... it doesn't matter."
Under any circumstances... hope turning 60 turns out to be a positive experience for you.