I'm 61, turning 62 next month. I'm happier than I've ever been. Good wife, good life, finances adequate, health nominal, what's to bitch about? I don't have to get up and go to work, don't answer to any psychopathic corporate assholes, and I've got many (maybe too many) projects going that keep me busy. There are certainly things I would change, but in the greater scheme of things they're relatively minor.
I think that as you age you become a bit more realistic, and learn to appreciate what you have without constantly striving for more. I know I'll never own a private jet or mega yacht, and that's just fine.
As I age I find I'm less concerned about the opinions of others, and that is
truly a good thing. If somebody doesn't like me or my opinions or the way I live my life they can just fuck the fuck off.
EDIT this doesn't mean it couldn't all turn to shit in a heartbeat, though. Debilitating disease, financial disaster, death, mega volcanoes, Ebola pandemic, thermonuclear war, any of those could put a damper on my day. But no point in worrying about things you cannot control. In the meantime there's beer to drink and new recipes to try, so eat, drink, and be merry, there's a long dirt nap at the end of the road for all of us.

A man who carries a cat by the tail learns something he can learn in no other way. - Mark Twain
The sky is falling! The sky is falling! - Chicken Little
I never go without my dinner. No one ever does, except vegetarians and people like that - Oscar Wilde