In Catholic theology, union signifies a profound relationship with God, achieved through divine grace. It's not merely a feeling, but a deep, transformative process. This union fosters spiritual growth, leading to a gradual moral transformation. Through prayer, sacraments, and virtuous living, one actively participates in this process, allowing God's love to reshape the heart and mind. This inner work isn't passive; it requires conscious effort, a commitment to self-discipline, and openness to the Holy Spirit's guidance. The journey is a path to holiness, a continuous striving for greater likeness to Christ, and a deepening of one's love for God and neighbor.