test your knowledge of regular skills and gain mastery

I completed some work procedures from memory the other day. This struck me as a great tool for personal development. Prove you know something to yourself by performing it from memory. You will gain confidence and uncover weak points that may remain in your understanding.

know the theory, gain the unfair advantage

Knowing the theory of a discipline gives you an unfair advantage when discussing related topics or particularly subjects that rely on the foundational theory. A recent story serves as an example. I joined a call discussing some work requirements. All the people on the call have been working with the current company and product longer than I. However, I contributed significantly to the conversation because I know more about accounting than most of my peers.