It's hard being human. A lot of cognitive ability peaks before age 25[1], physical before 35[2], and to some extent it's an inexorable downward slope from there. Accumulated experience often makes up for it, but only to a point. You still won't be as good as the version of you that started earlier, or learned faster. People reach 40 and finally start exercising and eating properly and miraculously feel 25 again - there are always ways to fight it. But they'd have been even more effective with the same habits at 25.

Life is stressful. There is fear of failure, there is fear of disappointing others, and ultimately there is fear of death. And that final deadline doesn't even have the courtesy to let us know when it will come.

But many people get nothing much done without a deadline. Most get more done with some time pressure. I'm not sure how we would manage immortality. If we lived twice as long, would we work half as fast? One hopes that for a little while at least, we manage to be happy and content with what we have.

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC4441622/

[2] https://pubmed.ncbi.nlm.nih.gov/17717011/

If what you value most is performing IQ tests, or competitive chess, then yes there is good data on the 25 part. If what you value is complexity and richness of thought, not so much.

Honestly if I exercised and ate perfectly from 20-29 I would've had a miserable 20s. Doing high-discipline stuff like that is way easier when you have a material reason (i.e. you've actually felt the consequences of not being fit or healthy) compared to when people just tell you "do it! you'll really thank yourself for it 20 years later!". Being in perfect physical condition at the cost of the psychological stress of forcing myself to do stuff I don't want to do every day does not sound worth it.

That’s one way to think about it. For me personally, a single evening with even driven and dedicated 25 year olds makes any claims of a downward slope like you describe laughable. At best, they’ll know one thing sort of well at that age. Most of the interesting stuff happens when you synthesize a lot more experience, and have the appreciation for time and wisdom to utilize it well. Whats the average age of startup founders, like 45? Average age of authors first books like 36-42.

Give me a break with that hustle culture.

Most people are complete dumbasses at 25. (I include myself at 25 in that assessment) So if this is peak intellectual capabilities something does not add up.