I spent twenty years playing V–I without hearing it. Then a jazz teacher asked me to sing the resolution, and the whole tonal system finally showed up.

The circle isn't a diagram on the wall of the theory classroom. It's the underlying current of a huge percentage of what we actually hear — once you learn to listen for it.

The ♭II chord is the one that made me realize borrowed harmony isn't an exotic flavor — it's a shortcut to somewhere the diatonic universe can't quite reach.