This document discusses the importance of retrospectives for continual learning and improvement. A retrospective is a ritual where a project team reviews the iteration/release/milestone to harvest lessons learned, identify successes and improvements. Insights from retrospectives form the basis for adapting and improving in future iterations. The document provides guidance on when to hold retrospectives, key questions to consider, and tips for successful retrospectives such as planning, using data, ensuring participation and building safety. Various retrospective activities are presented and the document emphasizes ending retrospectives well to begin future work well.