How to learn defense?

I’ve found that I play much (*MUCH*) better when I’m attacking vs defending. It’s at the point where I often make quite speculative or even dubious attacks just because of my greater comfort with taking an aggressive posture.
I’d like to develop a more balanced game, but am not sure where to start - we all know of the famous games showcasing effective attacking chess: the Immortal game, Opera Game, Kasparov/Topalov Fischer/Byrne etc., what games are considered defensive masterpieces (or does that question even make sense)?
I’ve heard Nimzowitsch’s profilaxis recommended, is this still considered a good place to start or has it been superseded by other works?