True happiness often stands in stark contrast to the material wealth celebrated by society. A deep, internal joy is placed within a person, differing greatly from the satisfaction others find in an abundance of grain and fresh wine [מצודת ציון, ביאור שטיינזלץ]. The primary approach among commentators suggests this joy is rooted in a noble love for others. While enemies and rivals might wish for a person's downfall and celebrate his misfortune, a truly refined individual holds no grudges. Instead, he finds genuine happiness in the success and prosperity showered upon his adversaries. God grants this profound kindness by placing a good heart within him, one capable of celebrating the well-being of others without a trace of jealousy. When a person chooses this selfless path, God actively helps and guides Him along the way [רד״ק, אבן עזרא, מאירי, ביאור שטיינזלץ].
Another perspective views this contrast as a comparison between two entirely different types of happiness. The general public often focuses its desires solely on physical success in this world, finding satisfaction only when their harvests and wine overflow. In contrast, God implants a spiritual, internal joy within the heart of the faithful. This profound gladness stems from a sense of contentment with one's lot and a deep connection to God. Ultimately, this spiritual fulfillment is far more powerful and enduring than any temporary excitement brought about by material wealth [מצודת דוד, מאירי, ביאור שטיינזלץ].
Looking at the same contrast from a different angle, the material prosperity of wicked individuals can actually serve as a source of hope and future joy. Rather than falling into despair when witnessing those who act wrongly achieve great financial success, a faithful person draws a powerful logical conclusion. If those who openly violate the will of God are granted such massive abundance in this temporary world, then the ultimate reward waiting for those who faithfully do His will is absolutely guaranteed and infinitely greater in the World to Come [אלשיך, מאירי].
From a more practical and national standpoint, this deep sense of gladness can also be understood as the relief that follows the end of a severe drought and famine. When the land's produce finally multiplies, the nation is freed from the burden of purchasing food from foreign countries. This newfound self-sufficiency allows the people to dwell securely in their own land and sleep in absolute peace [מלבי״ם].