The proverb presents a physiological and spiritual truth: the condition of the inner spirit directly affects the health of the whole person. Joy is genuinely healing — 'like a medicine' — not merely emotionally pleasant. A broken or crushed spirit, by contrast, produces a wasting effect that touches the entire person, body and soul. The inner life is not separate from the physical life.
Memory phrase: Joy heals like medicine.
Talk about it: How does a joyful heart help you?
Prayer: God, fill my heart with Your joy today.