He has chosen to use believers to accomplish His work of evangelism and discipleship. You know the kind of person you are. Willful sin, whether in action or attitude, gives Satan a powerful handle to restrict our usefulness in God's work. If I am not totally submitted to His will for me, He is greatly hindered in using me. Consider the absurdity of a carpenter attempting to construct a building with a hammer that wanders off every time he sets it down.
Sanctification is for service.
Sent into a dark, evil world with the pure Light. After the power has come, we become more effective witnesses. The root cause of these problems is my self-will. The cause of my complacency is my decision to remain complacent. Once this cleansing and energizing is accomplished, I will have an abiding hunger for Christlikeness.