The moment I understood the difference between (limb) independence, and interdependence.
It wasn't a specific lesson, and I probably didn't know what interdependence really meant, but I was watching a clinic, and something the guy did suddenly clicked with me. He was demonstrating independence by showing his left hand playing a 3-2 clave, against his right hand playing a 3-2 clave. He made it seem like there was a lot of concentration involved, and I don't think he was trying to fool anyone. But while sitting there watching and listening, I quickly figured out what he was doing, and it was very simple.
At that moment, I realized that how the limbs working with each other was more important than how they work independently. I don't think I knew the term interdependence at that point, but when I heard it, I knew exactly what it meant. And I also learned that once two limbs learn to work with each other, any limb can work with another without the typical left-handed or right-handed limitations.
FWIW, I never did use a 2-3 vs 3-2 clave, but I demonstrate it whenever I mention that clinic, and it translates even without sticks or drums.