John Calvin Commentary Psalms 30:8

"I cried to thee, O Jehovah; And unto Jehovah I made supplication:" — Psalms 30:8 (ASV)

O Jehovah! I cried to you. Now follows the fruit of David’s discipline. He had previously been sleeping soundly and fostering his indolence through forgetfulness; but now, suddenly awakened with fear and terror, he begins to cry out to God.

Just as iron that has gathered rust cannot be used until it is heated again in the fire and beaten with the hammer, so in the same way, when carnal security has once gained mastery, no one can cheerfully devote himself to prayer until he has been softened by the cross and thoroughly subdued.

And this is the main advantage of afflictions: while they make us aware of our wretchedness, they also prompt us to plead for God’s favor once more.