NOTES for Co2 7:10
Sorrow - heavy mood, connected with suffering. But the main thing is from what it results. Sorrow because of the impossibility to be in communication with God, when there is our sin between us and God, - without stopping being a painful feeling - is fruitful, it creates repentance restoring closeness with God, becomes salvific.
What is for God - the Only source of life and good, - is always fruitful, because only God can quench Godly sorrow, and complete all our waning.
If we sorrow on secular, which is to want what by definition does not have life in itself, but is exposed to corruption, then we can receive at the end only corruption.