Don't I know it. At 55, I learn more slowly and have to continually go over the things I have learned in the past to make sure I understand them fully. Take my time, don't get into a hurry, and think ahead so I don't lose my valuable info.
I remember when I was 55! Now I have a son who is 58 and another who is 52. Yikes!
I also have a brother who is 83 and has mid-stage Alzheimers, and living in a nursing home.
I have been blessed with most of my faculties still - except for the hearing part.
I have been trying to learn what I can about the terminal commands, but as you are experiencing, the info does not want to stick around without a lot of repetition.
One day at a time is my 'New Motto'.
Your comment 'don't get into a hurry, and think ahead' reminds me of a snippet I read one time in connection with driving a car:
"Why do the young folks drive so fast, like they don't have much time left? Hey, it's us old folks who ought to do the fast driving, because we know we don't have much time left."
Enough of this philosophizing from an OG
Old Geezer
TC