My personal belief is hang with kids. I'm 56 and I dread the day that my kids are out of the house (and it's coming).
My kid keep me young, keep me learning. I used to coach high school hockey, that was a blast.
Want to be happy? Don't get old. Want to not get old? Hang with kids.
There was some interview with a tailor in HK I think, he was pushing 100 and still working. He credited kids, he said they kept him young and interested.