Thomas Aquinas remarks that devotion is spurred mainly by considering God's goodness.  Directly, such consideration causes joy because the remembrance of God is so delightful, but it also causes sorrow because we do not yet enjoy God fully.

But devotion is also spurred by considering our own failings, and now the picture reverses.  Directly, such consideration causes sorrow because the remembrance of sin is so dreadful, but it also causes joy because we hope for God’s assistance.

St. Thomas concludes, “It is accordingly evident that the first and direct effect of devotion is joy, while the secondary and accidental effect is that ‘sorrow which is according to God.’”

-- Summa Theologiae, II-II, Q. 82, Art. 4

Tomorrow:  Emptiness in Christ?