Continual refinement is an important principle for sustainable development because it enables teams to both adapt to and anticipate change in what they are doing (their project) and how they are doing it. Teams break down their projects into short, manageable iterations. The advantage of breaking down work in this way is that complexity is much easier to manage in small slices, and immediate feedback from users provides the teams with a powerful way to change directions if they need to. In addition, teams employ regular retrospectives so that they can talk about their projects in an open and honest way. This allows them to make adjustments to their processes, which is equally important to sustainability because continual learning and improvement help ensure the project will last over the long term.