Some people stopped learning the day they got their diploma. You can hear it in how they talk at thirty.

A diploma is easy to mistake for a finish line, and plenty of people cross it and quietly stop. What shows up years later is not ignorance so much as opinions that never got revised, references frozen at a certain year, and a small defensiveness around anything new. Nobody decides this on purpose. It happens by default when nothing in the week asks you to change your mind.

Put one thing in your month that sits above your current level, a book or a class or a person who knows more than you. Keeping the muscle of being a beginner in working order is the whole trick.