What is internal vs external triggers?

Example: You sit down at your desk Monday morning and open Twitter before doing anything else. No notification pulled you there. No calendar event said 'browse Twitter.' A vague feeling — restlessness, avoidance of the first hard task, low-grade anxiety about the week ahead — fired the behavior automatically. That's an internal trigger. Now compare: your phone buzzes with a Slack message and you switch apps immediately. That's an external trigger. Same behavior (context-switching), completely different origin. Until you can tell the difference, you can't design for either one.

This concept is part of Trigger Design in the How to Think curriculum.