If the first characteristic is listed first because it is the first necessary trait of the heaven-bound, perhaps the second trait is also listed meaningfully: “Blessed are those who mourn” (Matt. 5:4). Could Jesus have been describing heartfelt repentance and remorse? I think so, especially since Scripture is clear that godly sorrow results in a repentance that is necessary for salvation (see 2 Cor. 7:10). The mournful tax collector Jesus spoke of who humbly bowed his head in the Temple, beating his breast and crying out for God’s mercy, was indeed a blessed person. Unlike the proud Pharisee who also prayed in the Temple, the tax gatherer left that place justified, forgiven of his sins (see Luke 18:9-14). I suspect that there were those among Jesus’ audience who, under the conviction of the Holy Spirit, were mourning. Comfort from the Holy Spirit would soon be theirs!
If Jesus was not speaking of the initial mourning of the repentant person who is just coming to Christ, then perhaps He was describing the sorrow all true believers sense as they continually face a world that is in rebellion against the God who loves them. Paul expressed it as “great sorrow and unceasing grief in [his] heart” (Rom. 9:2).