Your sweet story reminded me of when my son was starting piano lessons. He was five. His piano teacher had him trace around each hand and write the numbers 1 to 5 over the fingers to show which finger to use on the piano keys. So he neatly printed 1,2,3,4,5 over his right hand and then neatly printed 1,2,3,4,5 over his left hand completely in reverse! Talk about a mirror image!
Congratulations on your ah ha moment. May you have many more.