I'm sixty-one and I still feel the same as I ever did. My kids are all out of the house, but that's how it's supposed to be. They're happy, and we're still close. I used to joke to them that I didn't want to be a grandmother until I was past 50. We joke that they granted that request. Then I started saying I didn't want to be one until after 55. Again, they granted that request. Then I pushed up the (joking, of course) request to 60, so at this point I'm reasonably at peace with becoming a grandmother (although I'm really not looking forward to having more people to worry about).
BUT, my hair is pretty much still brown. I don't have joint "issues" (well except for some major knee/ligament injury that has nothing to do with age), and I love that my family now includes my daughter's husband and others, and that one of my sons is in a relationship. The family is growing, and I love seeing the people my kids have turned out to be. (Not a big fan of the fine lines under my eyes; but I'm grateful for my apparent good health - knock on wood - and for discovering how much "the same" sixty-one feels for me.)
Sometimes, though, I think people equate medical conditions with age; and I know that medical conditions can make a person feel "old". (My kids' father has lived with some for years.)
I'm not bragging or being "macho" here. I'm only hoping to point out that age, by itself (or at least the age that I've reached so far) doesn't always have to feel older (well, again, at least when there's not medical conditions factoring into the mix). On the other side of things, though, I think that I've had so many bad things go on in my life from the time I was twenty on, I developed a kind of fight about not letting time or anything or anyone else take more away from me and my life than "necessary". I don't know. Maybe if you get kicked in the head hard enough, often enough, and early enough, you don't equate the bad stuff with aging anyway. :/
Well, I know a lot of people who live the same kind of life they lived decades ago, sometimes have additional responsibilities with grandchildren etc., and then blame age when they're tired at the end of the eight-hour work-day. Heck, I used to be exhausted at the end of the work-day when I was twenty-six and single.
And (sorry for the long comment here, but...) something else, for me, was that my mother had been through a lot (including illness), and she thought she was old at forty. Then when she was in her seventies she said, "I wish I'd known then how young I was." My mother essentially felt old for the last thirty-plus years of her life - when she didn't have to. She passed away at seventy-six, so she felt old for about half of her life. At the same time, this was a woman who was up every day at - like - 5:30 or 6:-00, who took care of everybody-and-his-brother's kids, who cooked huge dinners for whoever was at her house and needed dinner, cooked huge holiday dinners, and helped all kinds of people in any number of different ways - so she wasn't "walking the walk" when it came to acting old. She was just "talking the talk" - or else "thinking the thoughts". And, she's not the only person over seventy that I've known to keep going that way she did, or to spend her time helping other people.