“Blessed are those who mourn, for they shall be comforted” (Matthew 5:4) This is the second beatitude, and it logically follows the first. If one is poor in spirit, liberated from the spiritual and physical lusts of this world, he will necessarily mourn and weep over the conditions of man.
The poor in spirit know how foolish and sad it is to be caught by sin, to be victimized by falsehood and evil, to be wedded to destruction and death. Viewing the realities of this world without God, the world captivated by its own vain imaginations, the world thinking itself rich and prosperous and needing nothing but in fact “wretched, pitiable, poor, blind and naked” (Revelation 3:17), the spiritually poor man can only mourn. Knowing what could be from God, and what is actually with God, he will mourn and weep like the prophets over sinful Israel, like Jesus over the corpse of Lazarus and the city of Jerusalem, (John 11:35, Matthew 23:37) like Jesus Himself in the garden, confronted by His own cup of suffering which was so senseless and cruel.
Blessed mourning for sin is essential to the spiritual life. But in the victory of Christ, it is not morbid or joyless. On the contrary, it is filled with hope, with gladness and with light.
As it is, I rejoice, not because you were grieved, but because you were grieved into repenting; for you felt a godly grief, so that you suffered no loss through us. For godly grief produces a repentance that leads to salvation and brings no regret, but worldly grief produces death. For see what earnestness this godly grief has produced in you… (2 Corinthians 7:9-11)
In his writings, Saint John Climacus (7th c.) follows this teaching of Saint Paul. It is the classical teaching of the Christian spiritual tradition. The end of blessed mourning is not despondency or remorse, it is repentance and salvation. It is the “mourning which causes joy.”
Mourning, according to God, is sadness of soul and the disposition of a sorrowing heart which ever madly seeks for that which it thirsts ...
Mourning is a golden spur in a soul which is stripped of all attachment and all ties ...
Keep a firm hold of the blessed joy-grief of holy mourning and do not stop working at it until it raises you high above the things of this world and presents you pure to Christ.
The fruit of morbid mourning is vain glory and self-esteem, but the fruit of blessed mourning is comfort.
He who is clothed in blessed and grace-given mourning… knows the spiritual laughter of the soul.
My friends, God does not ask or desire that man should mourn from sorrow of heart, but rather out of love for Him he should rejoice with spiritual laughter.
When I consider the actual nature of compunction, I am amazed at how that which is called mourning and grief should contain joy and gladness within it, like honey in the comb. (The Ladder of Divine Ascent, Step 7)
“So do not make a passion the remedy against passion,” says Saint Nilus of Sinai, “lest you anger… Him who granted you this blessing (of mourning and tears). For in shedding tears for their sins many people forget the purpose of tears, and getting into a frenzy, they go astray.” (Saint Nilus of Sinai, 5th c., Texts of Prayer)