I came across this one and it really spoke to me. I'm often thinking about how to optimize my career, project or code-base. But I am reminded that "play" is an important aspect of human development and understanding. The older I get, the more I "play" with things from my childhood: Lisp, 6502 processors, model rockets, etc. And I always find something new in the play and in work after play. It's as if unstructured play jiggles my brain-stem sufficiently that I can see new (sometimes better) ways to approach old problems.