An important indicator of good mental health is the ability to grasp, face, and accept reality. And most people understand this. Ask the average person whether they are a realist and the majority will reply that they are. Indeed, tell someone that they are "not being very realistic" and they will probably consider it an insult. But it isn't easy to be a realist. As T. S. Eliot famously wrote, "mankind cannot bear very much reality."
Animals are guided largely by instinct and imitation, but humans are guided by thinking and ideas. And this capacity for abstract thinking has led to astonishing accomplishments, allowing a species of hairless ape to develop literature, art, and science, to build computers and land probes on Mars.
Unfortunately, it can also backfire. The philosopher Bertrand Russell once remarked that fanaticism was the greatest enemy to civilized life; in other words, the obsessive, single-minded devotion to one set of ideas. Indeed, if the 20th century has taught the human race one thing, it must be the potential danger of the wrong ideas possessing the wrong minds; nationalism, communism, social-Darwinism, Islamic Jihadism, the Nietzschean ubermensch, and numerous other ideas have been used to excuse acts of appalling savagery and brutality.
Perhaps the best antidote is the so-called "scientific method," developed in 17th century England, Holland, and France. In essence, this means forming a theory and then measuring it against reality. If the theory, or idea, cannot be supported by evidence and proved through experiment, it must be discarded. Put another way, theories must adjust to new facts, not the other way around. And this scientific method has been extended into other areas of life. If reason and evidence can be given a central place in science, why not politics? Such thinking led to the writings of John Locke, the 17th century English civil wars, the 18th century Enlightenment and, ultimately, the American and French Revolutions.
But what about individual human psychology? Most people carry an internal 'map of reality'. In other words, they possess certain assumptions, prejudices, and stereotypes, then interpret reality to fit them. Such internal maps are formed partly through personal experience and partly through the influence of other people, who of course have maps of their own.
The problems begin when people confuse the map with the territory. Imagine that you are making your way through an unknown land with an old paper map as a guide. According to the map, an open field lies directly in front of you. But when you look, you see a deep, fast-moving river. Do you keep walking? Or do you ignore the map and look for a bridge? Obviously, you would look for a bridge. But when it comes to internal maps, people grow very attached. If reality conflicts with the map, they will often reject reality and plunge into the river! The key to good mental health is to make reality primary, not your ideas about reality.
To be happy and healthy you must learn to cope with change. If you stick to a set of rigid ideas, however, a conflict will arise between your assumptions and actual reality. Many people prefer their map to the real world and reject anything that doesn't fit. And they will stick to their map even when it is causing them harm. For example, imagine a man named Walter. Walter was born in 1922 and raised by poor Italian parents in a tough New York neighborhood. When he was seven, the Wall Street Crash occurred, bringing economic depression in its wake. His childhood was one of extreme poverty and violence. He learnt that the world was a dangerous place and that to survive you must trust no one, be quick with your fists, work hard, and save every cent. Later, Walter married and moved to San Francisco, becoming a successful attorney with a large income. But he never forgot his early years. Even though the 1960s were underway and America was enjoying a consumer boom, Walter failed to update his internal maps. He lived in a city of hippies and free love, but he remained aggressive and mean with money, thus alienating friends and denying himself the happy new life he might have enjoyed.
Realism is especially important when thinking about your place in the world. Or, to put it another way, the ego's place. The ego is that vague sense of being a subject or 'I' that thinks your thoughts, holds your memories, and experiences your experiences. And this ego derives its identity from memory and anticipation. You are who you are because of what you did in the past and what you hope to do in the future. Unfortunately, the ego is a fragile, finite entity forever seeking to escape destruction. Those who pursue fame and wealth are often pursuing immortality, though their real motive may be hidden from them.
Of course, such attempts are doomed. Everyone is going to die. But it isn't only the egotist who lives in denial of this. A healthier, more realistic cure is to see the ego in a wider context. The more deeply you can identify with something greater than yourself, the more peace you will enjoy.