About 10 days ago, I started watching “One Day in America,” a National Geographic series about what I consider the darkest day in our nation’s history: the September 11 attacks.

Watching the show has been an emotional journey, and even though the tears roll as I view an episode, I highly recommend the series.

Scenes from the show brought back a deluge of memories. Like many of you, every detail of that day stands out, a slow-motion vignette filled with chaos, frustration, anger and despair.

The kids were already at school and I was sipping my first glass of iced tea when a breaking news alert blasted across the television screen. A few minutes later, I watched in horror as a second airplane crashed into the second twin tower and, in that instant, the world tilted.

The school went on lock down. Communication was limited.

One of my good friends worked at the Pentagon and it took three days for us to connect. I prayed for his life and prayed for his family. I cannot imagine how helpless it must have felt to not know what was going on, if a loved one would walk through the door again or if you saw them for the last time when they walked out the door that morning.

That afternoon, I drove to an appointment in Norfolk. The silent sky appeared motionless and uncluttered, except for the lone celestial element, the moon rise, which cast its dissenting opinion. If ever the waning moon mirrored emotions on earth, its patience wore thin that day, frowning at us all.

It’s hard to believe that 20 years have passed since that fateful day. In some aspects, I am not sure our country has recovered. Despite our collective semblance of unity in the days following, an underlying sense of distrust seems to have lingered, simmering just below the surface, waiting to boil once more.

I think about President George W. Bush’s words that day and those that followed, about meeting tragedy with “the best that is in our country, with courage and concern for others because this is America. This is who we are.”

We didn’t really know when or what would happen next, if an enemy would stage another attack on our liberties. As Americans, though, we put aside differences and united for the greater good. It was a wakeup call that, as Colin Powell pointed out, showed “American spirit will prevail over this tragedy.”

It’s hard to forget that day because it exposed our vulnerabilities. Yet, patriotism and an overwhelming sense of empathy banded us together. Tragedy brought out the best in us, in our country.

We should never forget the sacrifices made by those who were unable to escape the Twin Towers or by first responders rushing to assist. We should remember how feelings of helplessness morphed into hope for a stronger resolve.

As we reflect on the events of that day, let us never forget the Americans killed that day or the nearly 6,000 individuals who were injured in the attacks in New York, the Pentagon and a field in Pennsylvania. Let us remember that another second on earth should never be assumed, so we should make the most of our living moments.