Grieve, mourn and wail. Change your laughter to mourning and your joy to gloom.Remember, this is directed at the sinner (the one who continues to live a habitual life of sin) and the double-minded (the one of two minds, two psyches, two souls). James' advice to these people is to grieve, to mourn, to wail. The laughing that has been going on, needs to cease and be turned to crying and gloom. Why? Without repentance, there is no salvation. Without a change of mind, and a change of action, there is no hope. All of the good times that these people are having and all of the waffling and floundering that is going on will only lead to imminent doom.
For what is our hope or joy or crown of boasting before our Lord Jesus at his coming? Is it not you? (1 Thessalonians 2:19 -- ESV) Three things mentioned here... "hope" ... "joy" ... "crown of boasting" ... Hope - What does Paul have his sights set on? Joy - What is it that brings Paul joy? Crown of Boasting - That Olympic Wreath of Glory that is placed on his head? It is these people. It is his children in the faith. They are Paul's Hope and Joy and Crown of Glory when Jesus returns.