Kaydia That looks like an interesting book, I took a quick look at the contents and there is a section called "Can we all be Mozarts?" which has piqued my interest.
Based on my starting age of 65, the message is basically that time is short, and I should hurry up and learn so I can get to the music I want to play. As long as it's not too complicated and won't take too much time to learn. I guess it's a good thing that I like simpler pieces.
I'm 63, so we're in similar territory when it comes to our brains being a bit less effective than they once were. I have a similar mindset about the pieces I'm capable of playing, in that I'm happy to play simpler pieces and have no aspiration to play complex pieces that students might study for a grade 8 exam. More than that, I actually dislike listening to pieces involving masses of notes played at crazy speeds, such as Flight Of The Bumblebee - they make me feel ill! I like simple melodies and slow romantic pieces, which is fortunate because I doubt that I'll ever be able to play fast moving pieces.
"Don't let's ask for the moon, we have the stars." (Final line from Now,Voyager, 1942)