Make room in your hearts for us. We have wronged no one, we have corrupted no one, we have taken advantage of no one.  I do not say this to condemn you, for I said before that you are in our hearts, to die together and to live together.  I am acting with great boldness toward you; I have great pride in you; I am filled with comfort. In all our affliction, I am overflowing with joy.
For even when we came into Macedonia, our bodies had no rest, but we were afflicted at every turn—fighting without and fear within.  But God, who comforts the downcast, comforted us by the coming of Titus,  and not only by his coming but also by the comfort with which he was comforted by you, as he told us of your longing, your mourning, your zeal for me, so that I rejoiced still more.  For even if I made you grieve with my letter, I do not regret it—though I did regret it, for I see that that letter grieved you, though only for a while.  As it is, I rejoice, not because you were grieved, but because you were grieved into repenting. For you felt a godly grief, so that you suffered no loss through us.
For godly grief produces a repentance that leads to salvation without regret, whereas worldly grief produces death.  For see what earnestness this godly grief has produced in you, but also what eagerness to clear yourselves, what indignation, what fear, what longing, what zeal, what punishment! At every point you have proved yourselves innocent in the matter.  So although I wrote to you, it was not for the sake of the one who did the wrong, nor for the sake of the one who suffered the wrong, but in order that your earnestness for us might be revealed to you in the sight of God.  Therefore we are comforted.
And besides our own comfort, we rejoiced still more at the joy of Titus, because his spirit has been refreshed by you all.  For whatever boasts I made to him about you, I was not put to shame. But just as everything we said to you was true, so also our boasting before Titus has proved true.
– 2 Corinthians 7:2-14 (ESV)
For I made up my mind not to make another painful visit to you. 2 For if I cause you pain, who is there to make me glad but the one whom I have pained? 3 And I wrote as I did, so that when I came I might not suffer pain from those who should have made me rejoice, for I felt sure of all of you, that my joy would be the joy of you all. 4 For I wrote to you out of much affliction and anguish of heart and with many tears, not to cause you pain but to let you know the abundant love that I have for you.
– 2 Corinthians 2:1-4 (ESV)
12 When I came to Troas to preach the gospel of Christ, even though a door was opened for me in the Lord, 13 my spirit was not at rest because I did not find my brother Titus there. So I took leave of them and went on to Macedonia.
– 2 Corinthians 2:12-13 (ESV)
Worldly grief is an expression of regret over opportunities lost, your difficult present circumstances, or personal embarrassment.
– Kevin DeYoung
4 Against you, you only, have I sinned and done what is evil in your sight, so that you may be justified in your words and blameless in your judgment.
– Psalm 51:4
Repentance is a pure gospel grace. The covenant of works admitted no repentance; there it was, sin and die. Repentance came in by the gospel. Christ has purchased in His blood that repenting sinners shall be saved. The law requires personal, perfect, and perpetual obedience. It cursed all who could not come up to this: “Cursed is everyone that continueth not in all things which are written in the book of the law to do them. It does not say, “he who obeys not all things, let him repent, but let him be cursed.” Thus repentance is a doctrine that has been brought to light only by the gospel.