Complaining not only ruins everybody else's day, it ruins the complainer's day, too. The more we complain, the more unhappy we get.
From their teenage years on, children are considerably more capable of causing parents unhappiness than bringing them happiness. That is one reason parents who rely on their children for happiness make both their children and themselves miserable.
Every poll about the Left, the Right, and happiness reveals that the farther left one goes, the less happy the person is likely to be.
Rather than dividing the world between good and evil, the Left divided the world in terms of economics. Economic classes, not moral values, explained human behavior. Therefore, to cite a common example, poverty, not one's moral value system, or lack of it, caused crime.