None of the agile methods are claimed to fit all development situations. A team should attempt to adapt the methods and practices to fit their specific needs. For that reason agile principles call for self-reflection on a regular basis in order to identify where and how to make improvements. While some systematic approaches on how to execute this self-reflection process effectively have already been proposed, little empirical evidence currently exists. This paper reports empirical results based on a study where a project team conducted a self-reflection process called “post-iteration workshop” in order to improve and optimize the adopted practices in an XP project. Both qualitative and quantitative data were collected from four 1-2 hour workshops. The results show that with less than 4% effort it is possible to hold postiteration workshops that significantly help to improve and optimize practices and enhance the learning and satisfaction of the project team.