the effect will be disheartening

Never – no, never – go about the house in a worn-out dress, a housecoat without a belt, or with your hair uncombed just because no one is going to see you. You will see yourself in a mirror, and the effect will be disheartening.

Milo, Mary Jo. Marshall, Jean King. 1951. Family Circle's Complete Book of Beauty and Charm. New York. Garden City Books. p.352