Here the word "heart" represents the person. Alternate translation: "When a person is joyful, his face is cheerful" (See: [[rc://en/ta/man/jit/figs-synecdoche]])
The writer speaks of a person being discouraged as if that person's spirit were an object that is broken. Possible meanings are 1) The "injured heart" is spoken of as if it were a person who broke the spirit or 2) a person whose heart has been injured will also be discouraged. This can be translated in active form. Alternate translation: "an injured heart makes a person become discouraged" (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/ta/man/jit/figs-activepassive]])