The Second Beatitude:

“Blessed are they that mourn, for they shall be comforted.”

The weeping about which the second beatitude speaks is first of all true tribulation of heart, and repentant tears for our sins, over our guilt before the merciful God (for example, the tears of the Apostle Peter after his renunciation).
For godly sorrow works repentance to salvation not to be repented of: but the sorrow of the world works death, said the Apostle Paul (II Cor. 7:10).
Tribulation and tears coming from misfortunes which befall us can be spiritually beneficial. For example, the death of one of our close ones can result in beneficial tears, if the sorrow is permeated by faith and hope, patience and devotion to the will of God. Jesus Christ Himself wept over the death of Lazarus. Even more so can tears and tribulation lead to blessedness when they are shed over the suffering of our unfortunate neighbor, if these sincere tears are accompanied by Christian deeds of love and mercy.
Worldly grief is grief without hope in God. It proceeds not from acknowledgment of one’s sins before God, but rather from disappointment in ambition, aspiration to power, desire for gain. Such sadness, characterized by despondency and despair, leads to spiritual death, which can also result in physical death, by suicide or simply weakness due to lack of will to live. An example of such grief is that of Judas Iscariot, the betrayer of Christ the Savior. As a reward for mourning the Lord promises that they that mourn will be comforted. They will receive forgiveness of sins, and through this, internal peace. The mourners will receive eternal joy, eternal blessedness.