Is anything more grieving to the heart then to watch those who love Christ mingling in dissension?

Yes. The knowledge that it's possible, and perhaps likely, that some or many of my friends will not be in heaven brings great grievance to my heart. The only consolation is that they will have chosen that path and that hell will be an act of mercy for them, since they would not be able to stand being in the presence of the splendor of God.