Create in me a clean heart, O God,
and renew a right spirit within me.
Cast me not away from your presence,
and take not your Holy Spirit from me. -Psalm 51:10-11 (ESV)
If you want to know what true repentance looks like, read the 51st Psalm. There you will see David who is truly grieved by his sin and begging God for forgiveness. He doesn’t just ask that God overlook a single transgression, but that He might blot them all out. David recognizes the fact that simply forgiving a sin along the way is not the answer to his problem; David needs to have a new heart. A clean heart. He needs a “right spirit” renewed in him.
As Christians, we benefit from the wonderful covenant of Grace that includes the indwelling of the Holy Spirit to convict us of our sin so we may acknowledge it and repent of it, returning to God and the peace that we can only enjoy in fellowship with Him.