What is repentance? And why does it matter? Here’s an excellent answer from Thomas Oden:
Through the English word repentance carries the nuance of sorrow for what one has done, it does not as adequately imply reformation of character as does the Greek metanoia. Hence it is a less powerful term than metanoia, which implies a fundamental behavioral reversal (Matthew 3:8; Acts 26:20; Hebrews 6:1, 6) Metanoia denotes a sweeping change of mind and heart to forsake sin altogether. Repentance is a “coming to oneself” (Luke 15:10), a voluntary change of mind, heart, and will of the sinner in turning away from sin.
Genuine repentance occurs only when one earnestly calls to mind one’s own misdeeds so as to elicit profound sorrow for sin so as to renounce and forsake sin. Repentance assumes a full commitment of heart and mind to the mortification of those sins that so easily besets us, and to the Spirit’s vivification of a new life. Lacking deep hunger for a fundamental change of life, mind, heart, self-understanding, and behavior, a surface repentance only becomes a new temptation to hypocrisy.
Repentance is incomplete or insincere if it does not resolve to lead a new life (2 Corinthians 7:10). It seeks a true and accurate recollection of misdeeds without false humility (Hebrews 13:18). It does not suggest loss of appropriate self-esteem but rather requires a higher valuing of oneself by becoming radically honest before God so as to put one’s feet on the way to recovery. It does not imply a diminishing of personal identity but an honoring and clarifying of one’s personal identity through candid self-confrontation (Hebrews 3:17).
The Spirit has come to dwell in the faithful to comfort, guide, witness, and to bring all our redeemed powers to maturity in all spiritual graces.
Repentance is the first step.