It is necessary to be aware of our spiritual poverty before one can become a Christian because God's offer of becoming rich is for the poor in spirit. It is only by admission of being lost, corrupt, sinful, morally sick, etc., and unable by his own, that one could see his need to be found, be cleansed, be forgiven, be healed, etc., by the power of the blood of the Lamb which was shed for the remission of sins and by the power of the Holy Spirit to live a Godly life. As the Lord said, they that be whole need not a physician but they who are sick.
To become a Christian, a person must be sorrowful for his own sins, his own ways, a Godly sorrow which leads to repentance, a change of mind seeking and submitting to obey the will of God in order to please Him and not himself anymore.
The common experience of Christians in mourning is the mourning for the sinfulness of the world, its idolatry, rebellion to God, the use of the name of God in vain which is prevalent especially those who claim to be Christians and yet practice idolatry, because unless they repent and turn to God, they shall persih.