Jeremiah was grieved for his people.  They had walked so far away from where God wanted them to be that their return seemed absolutely hopeless.  His was response was to mourn over the situation because of all that was to be lost.  There is a place for mourning in faith – particularly when people face the consequences of sin.  There is mourning over the life that they could be living if they simply submitted themselves to their heavenly Father.  It's this process of grief that motivates us to bring people to the cross.  If there isn't a grief over what is lost, then there is no motivation to bring people to Christ.  Is your heart moved by the sin of others?  Do you seek to bring them to the Lord?