Sin and Testimony of the Holy Spirit
When sin gains the upper hand in a believer, the consciousness of his or her forgiveness is blurred and the witness of the Holy Spirit loses its force. Our faith in Scripture increases and decreases along with our trust in Christ. The confession of the testimony of the Holy Spirit is so sublime and ideal that the reality of the Christian life often remains starkly inferior by comparison.
Herman Bavinck, Reformed Dogmatics: Holy Spirit, Church, and New Creation, vol. 1 (Grand Rapids, MI: Baker Academic, 2001), 598