Worldly “happiness” is merely subjective (i.e., emotional) and non-virtuous, ergo, non-moral, not to mention superficial and fleeting. The world seeks it directly as a feeling but cannot attain it because true happiness is a byproduct of morality (e.g., justice and righteousness). By comparison, biblical happiness is character-based. That is, true felicity is virtuous, ergo, moral. True, it involves emotions and desires, but it is more objective in that it rules out some emotions and desires, while universally praising others.
When we humble ourselves and obey God’s command to “seek first the kingdom of God and His righteousness” (Matthew 6:33, HCSB), we get both righteousness and happiness. But when we seek first our own kingdom and happiness, we get neither. Simply put, the pursuit of God is the pursuit of happiness.