No matter where you are and what you’re doing, your worst enemy is always with you—your ego.

“Not me,” you think. “No one would ever call me an egomaniac.” Maybe you’ve always thought of yourself as a pretty balanced person. But for any person with ambitions, talents, drives, and potential to fulfill, ego comes with the territory. Precisely what makes us so promising as thinkers, doers, creatives, and entrepreneurs—what drives us to the top of those fields—makes us vulnerable to this darker side of our psyche.

Freud described the ego with a famous analogy—our ego was the rider on a horse, with our unconscious drives representing the animal the ego tried to direct. Modern psychologists use the word “egotist” to refer to someone who is dangerously focused on themselves, with disregard for anyone else. Each of these definitions is true enough but of little value outside a clinical setting. The ego we see most commonly goes by a more colloquial definition—an unhealthy belief in your own importance. It is, as Bill Walsh put it, “where confidence becomes arrogance.”

Most of us aren’t egomaniacs, but ego is at the root of almost every conceivable problem and obstacle we have, from why we can’t win to why we need to win all of the time—and at the expense of others.

We don’t usually see it this way. We think something else is to blame for our problems—most often, other people. We are, as the poet Lucretius put it a few thousand years ago, the proverbial “sick man ignorant of the cause of his malady.” With every ambition and goal we have—big or small—ego is there, undermining us on the very journey we’ve put everything into pursuing.

Ego is the enemy of what you want and of what you have: Of mastering a craft. Of real creative insight. Of working well with others. Of building loyalty and support. Of longevity. Of repeating and retaining your success. It repulses advantages and opportunities. It’s a magnet for enemies and errors. The second you believe in your greatness, the artist Marina Abramovic explains, that’s the death of your creative career.

Pioneering CEO Harold Geneen compared egoism to alcoholism: “The egotist does not stumble about, knocking things off his desk. He does not stammer or drool. No, instead, he becomes more and more arrogant, and some people, not knowing what is underneath such an attitude, mistake his arrogance for a sense of power and self-confidence.” You could say they start to mistake that about themselves too, not realizing the disease they’ve contracted or that they’re killing themselves with it.

If ego is the voice that tells us we’re better than we really are, we can say ego inhibits true success by preventing a direct and honest connection to the world around us. One early member of Alcoholics Anonymous defined ego as “a conscious separation from.” From what? Everything.

The ways this separation manifests itself negatively are immense: We can’t work with other people if we’ve put up walls. We can’t improve the world if we don’t understand it or ourselves. We can’t take or receive feedback if we are incapable of, or uninterested in, hearing from outside sources.

We can’t recognize opportunities—or create them— if instead of seeing what is in front of us, we live inside our own fantasy. Without an accurate accounting of our own abilities compared to those of others, what we have is not confidence but delusion. How are we supposed to reach, motivate, or lead other people if we can’t relate to their needs because we’ve lost touch with our own?

Just one thing keeps ego around—since it certainly doesn’t serve any productive purpose. It is comfort. Pursuing great work—whether in sports, art, or business— is often terrifying. Ego soothes that fear. It’s a salve to our insecurity. Replacing the rational and aware parts of our psyche with bluster and self-absorption, ego tells us what we want to hear, when we want to hear it.

But it is a short-​term fix with a long-​term consequence. Which is why we must fight it.