If you're a knowledge worker doing Tyler Cowen calls an intellectual athlete training, you should use Anki or some other form of spaced repetition.

See the responses to Michael Nielsen's tweet here for all the other great folks that do this:

What are you waiting for?!? Download Anki today. https://apps.ankiweb.net/

Also see https://www.rhyslindmark.com/native-spaced-repetition/.