For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death.
Listen to the "Verse by Verse" episode covering this scripture.
In this passage the apostle Paul explains the difference between the normal human sorrow that people feel when they get caught doing something wrong, and the godly sorrow that truly makes a change in our lives that pleases God.
Worldly sorrow might be fleeting regret or a desperate wish that we hadn’t been caught. But it doesn’t lead to real repentance or change, so the person continues on without being forgiven and still being guilty of sin and worthy of the death penalty.
Godly sorrow is real and commits to change. Paul illustrates this powerful, godly sorrow in the example of the Corinthian brethren in verse 11: “For observe this very thing, that you sorrowed in a godly manner: What diligence it produced in you, what clearing of yourselves, what indignation, what fear, what vehement desire, what zeal, what vindication! In all things you proved yourselves to be clear in this matter.”
This is no fleeting regret, but a full-fledged, all-out commitment to change—to stop doing those things that God hates—and to seek God’s forgiveness. We must replace the thinking that leads to sin with the thinking that leads to righteousness.