It's a way to deliberately and wisely spend your available time after your daily commitments have been met. The Discipline is a 10 day period, known as a decade in which each day is dedicated to a specific focus
The Discipline comes from an article by @fet which was inspired by the Neal Stephenson book, Anathem. In it the Avout retreat from the outside world for defined periods (1,10,100,1000 years) to focus on long term study and contemplation