People won't have anything to believe in. People won't have anything to fight for. We have to keep up this insanity, or else we will have to face the reality of not being anything. If the Messiah ever did come and bring the millenium of peace we would find ourselves in a world that would be infernally dull. Our whole social structure would completely collapse if the human condition were suddenly reoriented around ideally high moral standards.
Self deception is very important for our personal lives as well.
Even when all else fails we can turn to a bottle of fermented or distilled drink that will chemically induce us into a state of denial. Of course there are other substances as well. Maybe in the end to be a citizen of a wealthy technically advanced nation is a bit like being first class on the titanic. Maybe the immigration pressures are a bit like seeing the hoards down in steerage escaping those compartments of our wayward ship currently taking on water. Maybe happiness is at the bottom of a whiskey bottle.