How did St. Thomas Aquinas connect happiness with knowing and loving God?

St. Thomas Aquinas integrated Aristotelian philosophy with Christian theology to explain that human happiness is ultimately found in the love and knowledge of God.12

Drawing from Aristotle’s concept of an ultimate end or goal (summum bonum) toward which all human action is directed, Aquinas argued that this end is necessarily connected with happiness. However, he Christianized this view by positing that true, complete happiness cannot be fully achieved during one's life on earth. Instead, he taught that blessedness consists formally in knowing God, a state of direct knowledge often referred to as the beatific vision, which is accompanied by the full love of God.123

While humans can experience a limited form of happiness in this life through virtue and friendship, the perfect reward of heaven is granted by God’s grace. Aquinas maintained that both humans and lower creatures possess a natural tendency or love toward God, and that supernatural grace serves to perfect and elevate these natural human abilities.12