Where were you on 9/11/2001? I was teaching a virtual class early in the morning from my home in Rio Verde, Arizona. Suddenly, my students started disappearing. I had 20 participants, then 15, then 10, then none. I kept teaching until I had covered all the content, because I knew my client was sitting in and I knew what he expected. My husband had tried to get my attention, but I just waived him off. I was too busy working to be distracted by whatever it was he was trying to tell me.

When I finished the webinar, I walked into the living room just in time to see the second tower go down. When I learned that a plane had crashed into the buildings, my first thought was that “some idiot” had made a terrible, tragic mistake. I simply couldn’t imagine that there were people out there who would do this sort of thing on purpose.

I didn’t know anyone personally who died that day, but the attack felt deeply personal all the same. I had a friend who was delivering a sales class in New York, just a few blocks away from ground zero. It was more than 24 hours before we learned that he was OK, but had been trapped with everyone else in the building behind a mountain of debris from the nearby blast. He walked for miles to get back to his hotel, where he was finally able to get to a land line and let us know he was alive and unharmed.

Today I can still close my eyes and see those terrible images that we all watched over and over again that day and many days thereafter. But I can’t for the life of me remember anything about the class I thought was so important to finish. I do remember that the client, even after we knew what was happening, insisted that I teach the next session that same morning, which was delivered to zero attendees. I also remember feeling very good when I no longer worked for that man a few months later.

That’s how memory works. The human brain doesn’t work like a camera. We select what we remember and what we throw away. We don’t need a day off from work or a formal minute of silence to keep the lost lives of 9/11 in our hearts. But I hope we never forget to find a few minutes for them every 9/11. That day taught us all that the rules were different. Everyone is fair game in a deadly contest that is still being fought. I lost the last vestige of my childhood innocence that day. I learned that there is such a thing as pure evil and that good does not always triumph over it.

In his work, The Persistence of Memory, Salvador Dali has intuitively captured many facts we now know about memory and the human brain. Far from being an accurate record of events, the brain’s recollection of past events is fluid, changeable and deeply subjective. In fact, not only do we know that no two people ever see the same event in exactly the same way, we also know that you will never remember an event in exactly the same way twice. Each time you trace over those neural pathways, new memories are enlisted to come along for the ride, and the total effect is altered. And yet, there is something consistent at the core of our memory, some emotional response that is often hard to to put into words. That is the part that remains, persisting after all these years.