The happiness which God designs for his higher creatures is the happiness of being freely, voluntarily united to Him and to each other in an ecstacy of love and delight compared with which the most rapturous love between a man and a woman on this earth is mere milk and water.
(C.S. Lewis in Mere Christianity on why God decided to create us with a free will, a will that could reject Him.)
For as the Father and the Son
and He who proceeds from them
live in one another,
so it would be with the bride,
for, taken wholly into God,
she will live the life of God.
(John of the Cross in Romances (trans. Kavanaugh and Rodriguez) reflecting on why God created the Church)
The Bridegroom' love, or rather the Bridegroom who is Love, asks only the commitment of love and faith. Let the beloved love in return. How can the Bride not love, the Bride of Love himself? How can Love not be loved?
(Bernard of Clairvaux, Sermons on the Song of Songs: Sermon 83 (trans. G.R. Evans))