> I'm willing to bet there are people over 65 doing all those things much better than you are currently able to.

Of course this is true, but my chances of being fit enough to engage in those activities at 65 go down with the passage of time, and from many factors outside of my control (accidents, major illnesses, something else...)

But there's a more subtle point. By the time I'm 65 I may not want to surf or mountain bike, but I do now.

I need to retire the 20 year old me, the 30 year old me, the 40 year old me .... so that I can enjoy some freedom at each stage of my life.

By the time I'm 65, I literally won't be the same person anymore.

Then decide right now that you want to be fit enough 30 years from now to mountain bike <insert local singletrack here>. What does that take? Probably the ability to pedal a bike with a heart rate of 150 for 3 hours. What does that take? You going out and riding a bike for 3 hours per day 2-3 times per week, every week until then. There ya go.

Not saying don't take the time to enjoy life now, but don't sell your future self short. Especially on fitness. I feel like it's "ok" to be unfit after 35 the way it's "ok" to be bad at math. Like somehow society agreed that both of those just don't matter.

The real problem is we have mechanized so much. Granted, machines can let us do so many things that would be utterly impossible without them, but the problem is we've allowed them to _substitute_ our natural labor and not to just _extend_ it.

Sure and I am doing that, but 'stuff' can happen.[1]

[1] And already has, at least to me.