To understand repentance, look at sin.
For true repentance to take place, one must have the sense of sin, i.e. he must be conscious of it. Sin is lawlessness (1 John 3:4). It is wrongdoing (1 John 5:17), and everyone does it (cf. Rom. 3:10, 23). If we say we have not sinned, we are not telling the truth (1 John 1:8, 10). The tragedy of our sinfulness is the greatest tragedy for it separates us from God (Isa. 59:1, 2). Admitting our sins is difficult because sin is so deceptive (cf. Heb. 3:13). But it always produces death (Rom. 6:23; Rev. 21:8). God knows our every sin (Heb. 4:13), so we must confess it and turn away from it to be right with Him.
Before true repentance can happen, there must also be sorrow for sin. “For godly grief (or sorrow, A.K.) produces a repentance that leads to salvation without regret…” (2 Cor. 7:10). Since it produces repentance, sorrow is not repentance. It is only part of it. The goodness of God should cause us to be sorry for our sins and turn away from them (cf. Rom. 2:4).
Moreover, for true repentance, there must be a severance from sin. Jesus told of a son who said he would not obey his father’s command but “afterward changed his mind and went” (Matt. 21:29). This He told to illustrate repentance. Repentance involves acts that can be seen and known. The king of Nineveh issued a proclamation that demanded, “Let everyone turn from his evil way and from the violence that is in his hands” (Jonah 3:8). And “when God saw what they did, how they turned from their evil way, God relented of the disaster that he had said he would do to them…” (Jonah 3:10). Later, Jesus said of that time, “they repented at the preaching of Jonah” (Matt. 12:41). Thus, repentance involves a visible change or turning. Paul said to Agrippa that he had declared to people “that they should repent and turn to God, performing deeds in keeping with their repentance” (Acts 26:20).
Repentance is a change of mind that results in a change of conduct (cf. Matt. 21:29).
–Andy