We may say that there are three reasons for which this journey made by the soul to union with God is called night. The first has to do with the point from which the soul goes forth, for it has gradually to deprive itself of desire for all the worldly things which it possessed, by denying them to itself; the which denial and deprivation are, as it were, night to all the senses of man. The second reason has to do with the mean, or the road along which the soul must travel to this union — that is, faith, which is likewise as dark as night to the understanding. The third has to do with the point to which it travels — namely, God, Who, equally, is dark night to the soul in this life. These three nights must pass through the soul — or, rather, the soul must pass through them — in order that it may come to Divine union with God… And, when this third night is past, which is the complete accomplishment of the communication of God in the spirit, which is ordinarily wrought in great darkness of the soul, there then follows its union with the Bride, which is the Wisdom of God.
–Saint John of the Cross (1542-1591)