When Jesus gives this beatitude, He does not say, "Blessed are those that have mourned" but "Blessed are those who mourn." He states it as a present and continuous experience. Repentance is not a one-time experience, nor does human nature, "the old man," simply disappear after we receive the new nature. Christianity involves a continuous learning and growing process. We are not instantly created in the image of God by fiat. God has decreed that we must live by faith, and that requires time and experience. We are created in the image of God through the fires of life's sorrows and adversities, as well as its joys. Even of our Savior, Isaiah writes, "He is despised and rejected by men, a Man of sorrows and acquainted with grief" (Isaiah 53:3). Paul adds,

Who, in the days of His flesh, when He had offered up prayers and supplications, with vehement cries and tears to Him who was able to save Him from death, and was heard because of His godly fear, though He was a Son, yet He learned obedience by the things which He suffered. (Hebrews 5:7-8)

The Christian is one whose mind is attuned to God's through an ever-deepening relationship. He has much to mourn over because the sins he commits—both of omission and commission—are a daily sense of grief and will remain so as long as his conscience stays tender. A tender conscience becomes hardened through the deceitfulness of sin. An active and growing relationship with God will lead to an enhanced discovery of human nature's depravity because God will faithfully reveal the massive gulf between His holiness and our corrupt and ever-polluting heart. He will make us conscious of the distance and coldness of our love, the surges of pride and doubt, and the lack of fruit we produce.