Getting Things Done

David Allen's 2001 productivity system book proposing a five-step method (capture, clarify, organize, reflect, engage) for managing all commitments and tasks through a trusted external system — freeing cognitive resources from tracking to doing.

Identifies that the anxiety of modern knowledge work comes from 'open loops' — commitments not fully processed into specific next actions in trusted systems — and provides the most systematic method for closing those loops and achieving stress-free productivity.