The human experience includes pain, sadness and loss -- no matter if one is righteous or wicked -- rain falls on us all at one time or another. One can be sad for the right or wrong reason. There are legitimate sorrows that are common to all humans and for which reasonable mourning is appropriate (losing a loved one, etc). The blessing of comfort that Jesus promises in Matthew 5 comes to a certain kind of mourner. Those who mourn for the right reason can be assured of the comfort of God. The sorrow Jesus speaks of here when He essentially says “Happy are the sad” is the unveiling of a different kind of mourning than this world deems relevant or useful.