I learned that using code as data is more powerful than anyone who hasn't used Lisp can understand. Unfortunately, most languages make it a pain in the ass.
I long for macros almost every time I program something in Python.
I learned that uniformity in good (by uniformity I mean the everything is a list feature).
I also learned that if you are mildly obsessive compulsive, (counting) the brackets will drive you crazy, and you will just give up.
Which led me to learn that if a language achieve type uniformity without syntax uniformity, it will be awesome, it will have all the goodness of lisp but with more forgiving syntax
I long for macros almost every time I program something in Python.