One of the greatest deceptions in the practice of the Christian religion is the idea that all that really matters is our internal feelings, ideas, beliefs, and intentions. It is this mistake about the psychology of the human being that more than anything else divorces salvation from life, leaving us a headful of vital truths about God and a body unable to fend off sin.The first 150 pages of this book do a great job in putting this point in context. The disciplines of which this book speaks are the ascetic practices such as (but not limited to) solitude and silence, prayer, fasting, simple and sacrificial living, and intense study and meditation on God's word. These ascetic practices were a vital part of the Christian experience of the first century church and modeled by Christ himself. However, over the centuries, the importance of employing spiritual disciplines in a healthy, balanced manner for spiritual growth has been lost or forgotten. Willard attributes powerlessness and ineffectiveness of the nominal (or should I say "normal"?) Christian experience of modern Westerners to the loss of the disciplines.
If you haven't read this book, I highly recommend it if you have the courage confront the conventional "wisdom" about the Christian life. This is a must read book for those who are committed to working out their salvation with fear and trembling (Phil 2:12).