Sorrow - such as arises from serious thoughts of eternity.
laughter - reckless mirth (Ecc 2:2).
by the sadness ... better - (Psa 126:5, Psa 126:6; 2Co 4:17; Heb 12:10, Heb 12:11). Maurer translates: “In sadness of countenance there is (may be) a good (cheerful) heart.” So Hebrew, for “good,” equivalent to “cheerful” (Ecc 11:9); but the parallel clause supports English Version.