“Good code invariably has small methods and small objects. Only by factoring the system into many small pieces of state and function can you hope to satisfy the ‘once and only once’ rule.” — Kent Beck, Smalltalk Best Practice Patterns, 1997.
This, for me, was the defining moment in software development’s evolution toward everything agile. The twin ideas of “lots of tiny pieces” and “once and only once” were game-changers. I’ve tried to live up to these simple words ever since, and I’m still learning today how to do it better and better.