In his classic, True Spirituality (a book I consider “essential and foundational reading” for every believer), Francis Schaeffer writes concerning the how of the Christian life.
“I became a Christian once for all upon the basis of the finished work of Christ through faith; that is justification. The Christian life, sanctification, operates on the same basis, but moment-by-moment. There is the same base (Christ’s work) and the same instrument (faith); the only difference is that one is once-for-all and the other is moment-by- moment. The whole unity of biblical teaching stands solid at this place. If we try to live the Christian life in our own strength we will have sorrow, but if we live in this way, we will not only serve the Lord, but in place of sorrow, he will be our song. That is the difference. The how of the Christian life is the power of the crucified and risen Lord, through the agency of the indwelling Holy Spirit, by faith, moment by moment.” (70)