Age and time. They catch up with the best of us. Despite its awesome capabilities, our brains are still finite apprehenders of reality. There is only so much knowledge we can each possess. And therefore, only so much knowledge we can retain or retrieve at any one time. Information that we used to have is changed, and therefore lost.
This is at once a threat to our existence. Loss of important information acquired in the past might cost us a bad choice. Effectively, we might make uninformed choices.
Here's sprinkling more salt on the wound. Losing information is one thing, but having our tuning for what's good or bad for us messed with, now that's something warranting some learned helplessness. At least if we forget, we can Google it now. But if we can't distinguish what's good or bad for us, even if it's staring us in the face, right under our noses, then Googling the most relevant hits will do us no good, pun intended.
So, how do we keep our senses tuned?