In order for the inner man to be strengthened with power through the Holy Spirit, the children of God must discharge their responsibility. They need to yield specifically to the Lord, forsake every doubtful aspect in their life, be willing to obey fully God's will, and believe through prayer that He will flood their spirit with His power.
Watchman Nee (1993). “The Finest of the Wheat, vol 2: Selected Excerpts from the Published Works of Watchman Nee”, p.50, Christian Fellowship Publishers