Is anyone taking care of an elderly parent, who is mentally sharp, but thinks he/she is cognitively impaired?

My father has been takings low dose of Ativan for the last 20 years. My dad, by the way, remembers everything. He reminds me to pick up dry cleaning, mail letters, etc. My point is he's sharp, but he doesn't think he is.

Sneak some Ativan into his coffee. Anxiety is just the beginning, he knows what is going on. He tries to remember a name or a number and just gets a blank reply from his brain. He's watched his parents and grandparents and knows he follows the same path. Uncle Mike said " Old age is not for cowards" and I had no idea what he meant until I hit 60.