Service is asking self to let go of the thing its holding to so tightly. If I find myself being inpatient with people or getting frustrated easily, then maybe I need to take time to serve people instead. I believe this same concept works with our possessions as well. If I find I'm getting stressed about money and I'm not obediently giving as the Lord instructs, then I need to serve others by giving more money and time to others. Service acts to bring us back into alignment with God's pattern for our lives. I know having been involved in church leadership that it can be difficult at times to love people in the congregation, to not be quick to judge or form misguided opinions about others. Those in these positions who practice service are reminded of the love of God for people and his desire for us to lead through serving. Willard indicates that this practice of serving will train us to exercise power without corrupting our souls. Willard indicates that this is why Jesus told his disciples to wash each other's feet (John 13:14).
Service to others bring humility. Service is the practice of self-denial which draws us closer to Christ. Service is a decision to obey God and serve him with our time and resources.