Ten years after 9/11, we cannot help but ask ourselves: What have we gained? What have we lost?

It is easy to tally our victories. The decimation of Al Qaeda’s leadership, including the killing of Osama bin Laden himself. The removal of a brutal dictator from power in Iraq. The thwarting of numerous attempted attacks on America and the West. Al Qaeda’s failure to mount another attack on the scale of September 11 anywhere in the world.

But our losses are more amorphous. They are best expressed, perhaps, in images. The crash of planes into a steel and glass tower, followed by the sight of tiny figures leaping, as if in a dream of flight, to murderously concrete ground. A symbol of America’s dominance and optimism reduced to toxic rubble. The end of an era when we thought we were invulnerable, and when we thought we were better than the rest.

The puzzling images have piled up since then. The photograph of Lynndie England, a Future Farmer of America, holding a naked Iraqi prisoner by a leash. Why naked? Why the leash? The bloodied faces of innocent children, children we had aimed to save. The images of soldiers weeping for what they had suffered, or for the suffering they had caused. The empty eyes of returning veterans, their spirits broken, as if they had lost their capacity to feel pain. When we think back to before, it hurts. Our optimism. The booming economy. The end of history.

It was impossible to believe that a tiny band of brainwashed thugs could have pulled off such a strike at a center of American power. And it was humiliating—so we lashed out at an Enemy. Never mind that it was the wrong enemy. Never mind that the weapons we used—bombs and tanks—were the wrong ones. We lashed out where we could, with the weapons we had available. In retrospect, it is clear we fell into a trap. Al Qaeda hoped to provoke America into direct military confrontation with a Muslim country, which it predicted would “expand the jihadi current.” And, for a time, it did.

War almost always results in foreseeable, yet unforeseen, atrocities. That is why when a president puts his nation’s youth at risk in war, he should be certain that there is a high likelihood of success, and that the anticipated gains exceed the likely collateral damage. There is no official figure for the number of Iraqis killed in the war, but Pentagon documents released by WikiLeaks show that U.S. military logs recorded 109,032 violent deaths between 2004 and 2009, some 66,000 of which were civilians. Since 9/11, nearly 6,000 U.S. troops have died in the wars on terrorism. Economists Linda Bilmes and Joseph Stiglitz have estimated that the total cost of the war in Iraq alone, including its impact on the economy, is at least $3 trillion. We face a long-term future of debt and deficit, which partisans attribute to the mistakes of the other side. No one seems to attribute it to our panic in the wake of 9/11, the trillions invested in our need to lash out.

There are emotional costs too. Service members who volunteer for war know that they are putting their lives on the line. But they and their family members may not realize that death for service members can come in unexpected ways. For example, it can come from what the military now calls “moral injury”—the shame that troops feel from having participated in or witnessed the death of civilians abroad. The Department of Defense reports 1,917 suicides between the years 2001 and 2009 among active duty military personnel, some of whom were no doubt burdened by moral injury. During that same period, the suicide rate across the services rose sharply, from 10.3 per hundred thousand service personnel, to 18.4. Suicide in the U.S. military has consistently been reported as a leading cause of mortality over the past decade. For veterans, the figures are even higher. More than 6,000 veterans take their lives every year, representing about 20 percent of American suicides annually. A study by the National Bureau of Economic Research says that the cost of treating soldiers’ psychological wounds from combat-induced post-traumatic stress disorder will amount to between $1.5 billion to $2.7 billion.

We did what we had to do in order to survive. Or so we thought. The nature of the threat made it imperative for authorities to focus on thwarting attacks before they occurred, rather than just responding to them. That, in turn, prompted us to curtail some of our citizens’ civil liberties. We felt compelled to torture suspects, or to look the other way when others practiced torture. Consequentialist arguments were made, and for many, they were persuasive. Nonetheless, the ethical compromises we made as a nation have changed us.

Was any of this predictable? It turns out that it was. The Pulitzer Prize-winning cultural anthropologist Ernest Becker wrote that humans are the only living beings forced to live with the knowledge of their own demise, at least as far as we know. That knowledge creates what the psychoanalyst Otto Rank and others called an existential anxiety. The best way to reduce this anxiety is to fantasize that we can become immortal through acts of symbolic creation—through our work, our religious or political affiliations, our culture. In recent decades, experimental psychologists Thomas Pyszczynski, Sheldon Solomon, and Jeff Greenberg developed terror management theory, which posits that all human behavior is motivated by subconscious terror of death, and the need to manage that anxiety through symbolic creations. We know, and are horrified, by our very corporeality, these psychologists tell us. As they put it in In the Wake of 9/11 (2003), we are

sentient pieces of bleeding, defecating, urinating, vomiting, exfoliating, perspiring, fornicating, menstruating, ejaculating, flatulence-producing, expectorating meat—that may ultimately be no more enduring or significant than cockroaches or cucumbers. The continuous awareness of these circumstances within which we live, faced with inevitable death, compounded by the recognition of tragedy magnified by our carnal knowledge makes us humans vulnerable to potentially overwhelming terror at virtually any given moment. Yet people rarely experience this existential terror directly. What saves us is culture. Cultures provide ways to view the world—worldviews—that “solve” the existential crisis engendered by the awareness of death.

The theory also posits that when people are reminded of their own deaths, they will more readily enforce their cultural worldviews. If their cultural worldview is xenophobic, nationalistic, or moralistic, they are prone to become more so. On a more political level, when Americans are reminded of their mortality, they view those who praise America in a more positive light, and those who criticize America in a more negative light. Patriotism is likely to increase, and punitive actions—including violence and war against those who criticize our worldviews—become more seductive. Hundreds of experiments have confirmed these findings.

Thus, U.S. leaders responded to the 9/11 strikes very much the way terror management theory would predict. We were reminded of our mortality. We lashed out. The costs for our nation have been inestimably high.

What now? The good news is that when we remind people of the good—or of anything that increases their self-esteem—before reminding them of their mortality, the negative impact is greatly reduced. And when respondents are reminded of their most important values—such as tolerance or their commitment to individual rights—mortality salience increases these commitments. If we are to prevail in the war on terrorism, we need to remember that the freedoms we demand come with great responsibilities. For one thing, those freedoms make us more vulnerable to terrorism. And these responsibilities involve not just fighting terrorists, but even more important, managing our own terror. It’s only by doing so as individuals that we can maintain our collective commitment to fundamental rights and tolerance.