Source: How do frequent emails and texts affect productivity? - Barking up the wrong tree
The secret number is 420. Times 3.
6 things that will make you more productive:
How can you stop e-mail from taking over your life? - Barking up the wrong tree
How to easily increase willpower and improve self-control:
5 Weird (But Effective) Ways You Can Conquer Chronic Procrastination