Proverbs 17:22 - Joseph Benson’s Commentary on the Old and New Testaments

A merry heart Cheerfullness of mind, especially that which is solid, and ariseth from the testimony of a good conscience; doeth good like a medicine Even to the body; it contributes very much to the restoration or preservation of bodily health and vigour, as physicians observe and experience shows; but a broken spirit A spirit sad and dejected; drieth the bones Wasteth the marrow of the bones, and the moisture and strength of the body.