Francis Schaeffer, of his own testimony, writes:

“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…  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.”

An important -even essential – distinction. It’s not just for the sake of doctrinal precision. It makes all the difference in how we live out our lives.