A person's inner emotional world inevitably spills outward, shaping both their physical appearance and their overall vitality. When the heart is full of joy, it radiates and brightens the face. The primary approach among commentators is that the heart serves as the root of the body and the source of its energy; therefore, inner joy naturally spreads to make a person's face shine with beauty [אבן עזרא, מצודת דוד, עמנואל הרומי]. In contrast, internal sadness leads to a crushed and depressed spirit [מצודת ציון, מצודת דוד, ביאור שטיינזלץ], which physically manifests in heavy sighs [עמנואל הרומי].
Beyond physical appearance, the state of the heart directly affects a person's mental and spiritual abilities. A joyful heart sharpens the mind and sparks a desire to seek knowledge, whereas sadness and a broken spirit block a person from learning and growing [אבן עזרא, רלב״ג]. Furthermore, joy is a strict requirement for receiving divine inspiration, as anger and sadness drive away the presence of God. For example, Jacob lost his divine inspiration during the years he mourned for Joseph, and the prophet Elisha required a musician to bring joy to his heart before the hand of God could rest upon him [רלב״ג].
From a social perspective, this dynamic can also reflect class differences. Joy and a bright face symbolize the wealthy, while a broken spirit and a constantly sour expression are the burden of the poor [אלשיך]. Taking a completely different approach, another perspective separates outward happiness from true inner spiritual health. Someone who is only happy about material success while ignoring their spiritual shortcomings may have a bright face, but deep down they possess a low spirit trapped in worldly desires. On the other hand, a sadness of the heart that comes from genuine pain over one's sins and spiritual flaws actually lifts the spirit higher [מלבי״ם].
On a theological level, these emotions extend beyond human feelings to describe the relationship between people and God. If a person walks an honest path and brings joy to God's heart, God will, in turn, shine His face upon them and fulfill their desires. However, if a person's actions bring sadness to God, they will encounter a broken spirit in the form of divine anger, much like the generation of the Flood [רש״י].