Happily, in this day and age, we have the ability to live healthy and active lives longer than previous generations.
To throw in the towel when we're still in our 50s is a bit premature. Keep going! Get out there and do stuff! Exercise, learn new things, try new things, enjoy life!! It's not time for the walker and rocking chair yet.
Maybe 70-something might be old ... but 50-something is nowhere near old yet.