But I'm not perfect. I'll miss a detail, I'll get a message in the chatroom, I'll take a stretch break. I'll forget. That's not just me being 40, that's me being human.
There's also the fact that when you're younger your body lets you get away with "murder": Drink lots of coca cola, eat junk food, sit for hours, never hit the gym. An apt metaphor would be that you had a 10k PC for gaming and lots of games that were not optimized properly but run well enough due to the hardware being that good.
The older you get, the more your bad habits bite you. So it's not just age decline but every lack of maintenance and abuse of drinking, smoking, junk food comes to take its toll. You know, the "I can do that while I am young" kind of habits.
What I'm saying is, it's more than aging that it's at fault. We just like to correlate aging with it because it takes years for the side-effects of all the poor habits to manifest themselves to take effect.