Matthew 5:4
"Those persons who feel grief [over their sins] are blessed because they will receive comfort [from God when they repent].
John 16:20-22
Truly, truly, I tell you, you will cry and mourn [i.e., over my suffering and death], but the world will be glad [about it]. You will be sad, but your sadness will turn to joy [i.e., when learning of my resurrection].
2 Corinthians 7:8-11
For even though I caused you sorrow by my letter [Note: Paul's writing of I Corinthians to correct abuses at Corinth apparently produced sorrow for their wrongdoing], I do not regret it, though I did regret it. [For] I see that my letter hurt you, though only for a short time.
Galatians 6:9
And we should not become tired of doing good things, for eventually we will receive [never ending life] if we do not give up.