Mid 20s on the decline

Perhaps you are not as fast a learner at piano as you have less time to practice it than you used to? Are you able to excercise to the same extent that you were in your teens? I feel like this probably isn’t you breaking down as a person but your lifestyle changing.

hahahaha....no worries kid, you will adjust by the time you enter your thirties and then a whole new set of realities will hit you in your 40's. I imagine this cycle repeats itself every decade. I guess the bigger question is how much time has passed since you regularly did the things you feel are declining. Do you play piano every day? Are you working your body to be agile every day? If you don't keep exercising your body and brain it will naturally decline.

This is why learning a language becomes harder as you age. At the age of 10 you are the apex of learning new things. Of course you spend that time learning the fundamentals of everything from then on through highschool. You are simply losing the quick ability to learn. That's not a problem If you are in a field that is your career or you have a intrest into something else. All the auxiliary learning is starting to fade that's it.

Change like that should be so gradual that you hardly notice. Please go visit a doctor.

Lol, 24... wouldn't worry about your age dude. Are you drinking/smoking a lot? Are you exercising enough? Eating healthy? Getting enough sleep? Is your mental health okay? Those are things I would ask myself first before feeling "old" at 24...

You might be overthinking it, but it also does sound like it is not a common thing.

Probably just adjusting to being in the adult world where things basically suck.
Most of life is drudgery. You are either working or someone is on your ass about getting a full time job and doing all those adult things.
I always said that sometime between age 18 and maybe 22 is when we get the reality slap. That slap is when we finally figure out we are no longer a kid and are adults. It kind of hits hard and sudden. It doesn't happen the day we graduate high school or turn 18, but soon after.

So unless you have started using drugs or alcohol on a regular basis, it is just growing up. It is hard to enjoy life or have as much fun doing anything when that reality hits.

You're gonna die soon, it's a brain aneurysm.

I'm 25 and I feel the same as I did when I was 19. But everyone functions/ages differently maybe it's your diet maybe it's something that is stressing you it could be a long list of things.

You are becoming a vegetable. Get out of your basement and play with the big dogs.

Do u have any diseases? Do u do any drugs or take any meds?

Lol 24 and thinking you're 70.. damn if this is for real, you might have a neurological condition because what you say isn't normal.