This document discusses how agile practices can result in an approach that is disciplined, sustainable, grounded in reality, and effective. It argues that agile is not the easy way out, but that processes like pair programming, testing, continuous integration, and retrospectives form a rigorous structure that holds teams accountable. When teams select their own processes, it empowers them and makes the approach sustainable over the long run. Agile allows teams to be adaptive, embrace opportunities, and deal with issues as they arise.