It's tempting to want to permanently banish those who stumble badly. But what is the ultimate aim of church discipline? Paul's focus is on mending, not just punishing.
The phrase 'this punishment... is enough' signals a shift. The corrective action had served its purpose: to bring the individual to a point of recognizing their sin and hopefully, repentance. Paul's heart, and God's heart, is for the lost to be found, the broken to be healed. He doesn't want the person to be 'swallowed up by excessive sorrow' (2 Corinthians 2:7), which would be counterproductive to restoration. The church's role is to apply God's loving discipline and then to confirm their love and welcome them back.