When a believer who has fallen into sin responds to God’s call for repentance, he or she should place laughter and joy aside to reflect on the sin with genuine sorrow (2 Cor. 7:9, 10). In James 4:9, laughter seems to refer to the loud revelry of pleasure-loving people. They immerse themselves in a celebration of their sins in an effort to forget God’s judgment. A Christian should never laugh at sin.
However, Christian sorrow leads to repentance; repentance leads to forgiveness; and forgiveness leads to true joy over one’s reconciliation with God (see Ps. 32:1; 126:2; Prov. 15:13).
Radmacher, E. D., Allen, R. B., & House, H. W.