Or while bicycling: “Always keep the rubber side down.”
Seems like no matter how much I practice, my fingers just won’t get up to speed on faster guitar riffs. It’s very frustrating for someone who was always very nimble and coordinated. My balance and coordination is still good at 70, but the combination of arthritis and age in my hands has taken a toll. Asking me to barre a chord is sort of like asking me to stick a needle in my eye.
Reminds me of a classic Car Talk puzzler.
An old guy just could not get his push lawnmower fixed to where it worked as well as before. Used to be he could mow the lawn with one tank of gas, but lately it requires two tanks of gas to get the job done. No-one could find anything wrong with the mower…
I’m more interested in why young people move so slowly. I’m 50, and I’m constantly frustrated by teenaged and 20-something coworkers just shuffling around and getting in my way because they walk so damned slowly.
Perhaps I can add something here. I’m an ex-amateur racing driver who is well into my 7th decade now so I do pay more attention to changes in driving behavior than most people. As for myself I have the usual squeeky joints and wear and tear but vision and hearing are still good. Balance is becoming a problem (like standing on 1 foot while taking your pants off) and caution when using stairs especially coming down. That being said I notice that in traffic I’m not quite as aware of whats going on around me. It’s not peripheal vision as much as not being “in the moment” or situational awareness. However when driving on winding roads I would guess that I’m nearly as quick as far as reflexes go as I was in my 20’s. If you have confidence in yourself in a car it doesn’t really go away but you do become more cautious in ordinary city traffic situations and therefore slower. On highways or freeways I’m very comfortable at 80-85 most of the time.
Impaired vision, slower reflexes, shorter attention span, tendency to be easily distracted. The real danger is the people who continue to drive fast, in spite of these factors.
There’s also time dilation. Time goes so much faster when you’re older. So if it takes you an hour to get someplace, it seems like 15 minutes. So if you’re driving at half the speed, you’re actually driving faster.
Well, it took you four and a half years to respond to me. Did it seem like 15 minutes? 
I’m in my late 60’s and (I think) in quite good shape - I play soccer with the whipper-snappers 3X a week and exercise at the gym 3 more days.
While I don’t feel my walking has slowed down, I do get an appreciation for what its like when I get the occasional injury.
So even though I get frustrated behind the slo-goers (and know I shouldn’t) I get some appreciation for what its like.
And that’s just for obvious physical limits - not to mention all the other causes that can contribute.
What I do mind, though, are the folks young or old, who don’t exhibit basic courtesy in the motion department. Example - the other day a person with limited motion (OK - I accept that) finished checking out at the grocery line, but then stood there blocking the line for a couple minutes while fiddling with her purse, getting car keys, whatever. The cashier couldn’t even start checking out the next customer. Limited motion or not all she had to do was step aside and let everyone else through.
I’m 79 now and have been running for over four decades (taking time off to eat and rest :)). Races have age groups for an obvious reason: Past a certain age your speed diminishes. That is a irrefutable truth. I’ve read the reason is the loss of fast twitch muscles, but I read years ago in a scientific journal (don’t remember which one – memory loss due to aging? 
- perhaps the Lancet)) that it is not the loss of fast twitch muscles but the conflation of them so they more resemble slow twitch.
I am 67 (gawd, it is so strange to think of that…). I have osteoarthritis (I really wish I didn’t know how to spell it) since 2005.
I use a CPAP. One morning I awoke to find the hose (a bit over an inch in diameter) woven between the fingers of my left hand. This is the only trigger I know of.
My left pinky will no longer bend straight - it curls under the ring finger.
Now the ring finger is getting into the act.
My left hand is turning into a claw.
This is the kind of crap common to old farts.
So far, my pelvis and legs are unaffected (aside from atrophy from non-use).
Not all of us get even that small blessing.
If my legs acted like my hands, shoulders, and elbows, the remarkable thing thing would not be that I walked slowly. The remarkable thing would be that I walked at all.
Old witticism: “Do not worry about killing time - time is killing you”.