It's a system to save us from our endless to-do lists, which can turn any job into a lifeless chore. It works on two principles: 

Visualize your work and limit your total number of "works in progress."

• Create three columns on a board where you can use magnets or post-it notes. Label the columns: Options, Doing, and Done.
• Write your individual tasks down on separate cards. Post all of these cards in the "Options" column.
• From that column, choose no more than three to move...

Starting but not completing too many projects puts people at risk of the Zeigarnik effect, which states that people are better at remembering unfinished tasks than completed ones.