As Grandpa used to say "I don't remember as good as I used to but I can remember once as good as I always did" or something like that. I can't remember for sure.
An old boss/friend of mine quipped “Yeah - having a bad memory sucks. On the other hand, my wife is going to let me hide my own Easter eggs this year!”
The funny part was, he could remember scientific details from projects he had done 50 years ago!
A lot of grandpas used a similar line when referring to their waning sexual prowess - “I’m not as good as I once was, but I’m as good once as I ever was.”