Before 9/11 from time to time we might have mused: What if you found out you had a hour to live? Who would you call and what would you do? On Sept. 11, 2011, and afterward, we saw what people chose to do when death stared them in the face.

Colleagues and friends stayed in fiery buildings with their office mates or went back to rescue them. The defense secretary went to drag employees out of the Pentagon. Firefighters rushed into burning buildings. A mayor seized the city and the country by the scruff of the neck and prevented abject panic. A president in the days that followed found his purpose and delivered some of the most compelling rhetoric in presidential history. Men and women left the safety of home and the embrace of loved ones to fight wars with determination that their countrymen sometimes lacked. For 10 years we’ve seen example after example of grace, courage, kindness and decency.

Sept. 11 stays with us not only because it was among the deadliest days in U.S. history, not only because it changed the nature of the fight against jihadists, and not only because it revolutionized our intelligence agencies and military, but because it was an event with profound moral consequences. In a world of moral relativism we had an experience that defined our enemy and ourselves. They are for death; we are for life. They are for domination; we are for tolerance. It elevated heroic, dare I say “manly,” qualities in a free people who had been accused of going “soft” and it challenged us to be at least a faint echo of the best citizens among us.

There was before 9/11 and there is after 9/11. For thousands who lost parents, children, spouses, siblings and friends, the atrocity marked a gash through their lives. Before they had their loved ones, and then they didn’t. For the rest of us (but unknown to our younger children), before there was the utter ordinariness of airplane travel, the “end of history,” the landmark Twin Towers and peace. And then there was the maddening hassle of flying, the battle for our civilization, the open wound at the base of Manhattan and war. The raft of “forget 9/11” or “look how we injured ourselves since 9/11” thumb-sucking commentary is, perhaps, the futile effort to turn the clock back. We feel deprived and want our pre-9/11 world back again.

The day is about loss. But besides mourning, it is also an occasion for gratitude. We marvel at the good fortune to live among citizens who risk life and limb for one another. We are thankful for the gifts of liberty and decency in a country of unparalleled goodness.

The serendipity by which some live (missed the bus, went to drop the kids off at school) and others die (had the meeting at Windows on the World) can be horrifying. But it reminds us to cherish life and those we love. Never part without a hug or kiss or an “I love you.”And never take any of it for granted.