This past Sunday, Americans gathered to memorialize the 10th anniversary of Sept. 11, 2001. As a nation, we collectively remembered the shock, the anger, the grief and the loss felt when we saw the World Trade Center towers collapse – but we also remember the solidarity emerging in the midst of that dark day.

It was the first domestic tragedy of our generation, and 9/11 went down as the worst act of terrorism on U.S. soil in history. At 8:46 a.m. Eastern Standard Time, terrorists flew American Airlines Flight 11 into the North Tower of the World Trade Center; the first plane was followed 17 minutes later by United Flight 157, which crashed into the middle of the South Tower. At 9:37 a.m., American Airlines Flight 77 was flown into the Pentagon by five hijackers. But the passengers of the fourth intended flight, United Flight 93, upon realizing that their plane was being hijacked and hearing what had happened with the three attacks earlier in the morning, banded together to fight back against the terrorists. Their efforts resulted in the terrorists being diverted from their course towards Washington, D.C., crashing the plane instead into a field near Shanksville, Penn.

The passengers and crew of United 93 were not the only heroes on that day. Legions of public servants — firefighters and police officers, in particular — gave tirelessly of their time, and even gave their lives, to rescue people from the blazing heaps of metal that littered the World Trade Center. America came together on that day and in the weeks that followed, putting aside whatever differences they had in favor of uniting in action and in support of the nation and the lives that had been lost.

That sense of unity, of a higher calling, enabled this country to endure the terror of 9/11. Much has changed in the last decade because of those attacks, and the events that have unfolded in this time reveal, however, that many of the lessons of 9/11 attacks have been ignored or forgotten. It didn’t take long before America returned to political infighting, unnecessary wars and the hatred of a people whose only crime was to share the same color or religion as those who had attacked us. When we remembered 9/11, it seemed, what we called to mind was fear rather than strength; vengeance rather than solidarity.

We all have our own memories of that fateful day. But however varied our remembrances may be, however young or uncomprehending we were on that day, one common thread connects us all as we look back on 9/11 a decade later: a longing for security in the face of terror, for peace born of the ashes of Ground Zero.

In the days immediately following Sept. 11, 2001, America and the free world stood united against such reckless acts of violence. The anniversary of the attacks on the World Trade Center is a time to remember and stand for not only the 2,996 that died that day, but all victims of terror. It is a time to remember that terror did not begin and it certainly did not end with Sept. 11, but grows where ignorance and fear hold free reign. Terror begets terror, whether it is committed by fundamentalist car bombs or drone air strikes on remote villages. For thousands upon thousands still, our 9/11 is their 24/7.

For too many, terror is not merely a memory or a list of names.

So for all who remember, in all our varied ways, let that memory be a call to not only mourn the past — but a call to stand for the future, so that present horror may, too, one day become only memories.