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/