Willard goes on to identify a fundamental, crucial point brought out in Jesus life that the "activities constituting the disciplines have no value in themselves. The aim and substance of spiritual life is not fasting, prayer, hymn singing, frugal living, and so forth. Remember, it is the effective and full enjoyment of active love of God and humankind in all the daily rounds of normal existence where we are placed. The spiritually advanced person is not the one who engages in lots and lots of instruction or punishment." I think Jesus makes this point to the when asked about fasting in Matthew 9. The followers of John and the pharisees were fasting, but Jesus said now is not the time to fast because I am with you. In other words, we don't fast just to partake in a spiritual ritual.
When I read Willard's comments here, I can't help but think that a life in Christ is meant to be a full enjoyment of the active love of God and humankind where we are placed. This is the aim of the spiritual life. Following Christ is not a chore, its not dull and lifeless, and its not something we do out of obligation. Self gets in the way, self must be overcome so that we may live fully in Christ - this is the purpose of spiritual disciplines.