I was 12 years old and in school just a few blocks away from the World Trade Center on September 11, 2001, when we felt the impact of the first plane hit the first tower.
Unaware of the events unfolding outside, my class continued with our science lesson, until an announcement commanded everyone to move to the cafeteria. We waited there, confused and frightened, until the bomb squad burst in and told us we had five minutes to evacuate the building.
Parents rushed into the cafeteria, frantically searching for their children. I panicked, wondering how I would get home to my elderly grandparents, who lived in our apartment building several blocks from the towers, when my neighbor and her 13-year-old son appeared in the doorway to walk me home.
We left just minutes before the first tower fell.
We ran for our lives away from the collapsing towers — the first, then the second. I'll never forget what we saw, heard, smelled, and experienced as we pushed through crowds of bloody, ash-covered bodies and a sea of police officers toward home.
It seemed like the world was ending, and although my parents and I had survived, the world as we knew it would not — life after 9/11 was just beginning.
In the days that followed, our neighborhood became a war zone. We avoided going outside as much as we could because the air was full of toxic smog. We had almost no access to food, water, phones, electricity, or medications.
Armed National Guards were posted at every corner. The towers were still on fire and more bomb threats and building collapses were rumored seemingly every hour. I didn't have school for two weeks, and when we were relocated to a school further uptown, we were encouraged to move on and focus on school.
But "moving on" was not easy in the era of orange alerts, anthrax scares, "weapons of mass destruction," and shoe bombs.
For years, we survivors grew up physically ducking as planes flew overhead. A siren, a scream, or a bus passing over a speed bump could send us into a state of panic. These sounds are as common in New York as the sound of crickets in the country.
But it wasn't just our worlds that were changed forever — it was the world:
This was the beginning of the "If you see something, say something" campaign by the Department of Homeland Security, which encourages citizens to report suspicious or unattended bags that could be bombs or otherwise dangerous.
Two months after the attacks, the Transportation Security Agency, or TSA, was born. Your friends and family could no longer meet you at the gate — only ticketed passengers could get that far. New scanning equipment was introduced. Plane cockpit doors were reinforced to "withstand a grenade blast," and usually remained locked throughout flights.
Coming back from a trip to Disney World the following spring, I was terrified in the airport because a baseball team was being loud and rowdy, which triggered my PTSD.
Later, a man on the plane kept telling passengers to "look out for" sitting in first class, but he didn't explain why. I was immediately suspicious, but after a crowd of people gathered around a man at baggage claim asking for autographs, I realized Yankees pitcher Ramiro Mendoza had been on our flight.
TV shows like "Sex and the City" and movies like "Spiderman" that featured the towers in one way or another were changed to edit them out post production.
The media publicized the identities and background of the terrorists, which led to a spike in hate crimes against Muslims and people who appeared to be Middle Eastern in the US, as the New York Times reported.
Fortunately, I had a humanities teacher who helped us to better understand exactly who was and wasn't responsible and where information was being distorted, but trying to wrap your head around all of it at age 12, in the face of more threats, was overwhelming and terrifying.
Previously, none of us really paid attention to planes. They flew over New York all day, every day, by the dozen.
After 9/11, I started instinctively ducking when I saw planes overhead, and neighbors often commented nervously on how low they were flying.
Survivors of that tragic day realized at a very young age that our parents, the government, and emergency medical personnel couldn't protect us from everything.
Many of us no longer felt safe or trusted those who we normally rely on to protect us. When I left for school, I was no longer sure whether I'd make it home to my parents after.
While these feelings were prevalent for all of us in living downtown and others in New York City, they also reached people as far as the West Coast, the Midwest, the South, those whose parents traveled for work, people who worked in high security buildings, pilots, and more.
In the months following the attack, thousands of people lined up to see and take pictures of the massive pit in the ground filled with wreckage where the the towers once stood.
Many took photos in front of the hole, smiling and posing, as if it were not a site of death, destruction, and tragedy. Street vendors sold books filled with images of the fireballs, the collapse, and the planes, like souvenirs you receive after a Broadway show.
Everyone in the world was flocking to what was essentially my backyard to look at the tragedy like it was a tourist attraction, and it remained this way for years.
Now, people can visit the Reflecting Pools, 9/11 Memorial and Museum, and the Freedom Tower.
On the other side of these tragic changes, and years of reeling from PTSD, came hope on the other side. That, and gratitude, at least for me — for my own life, the lives of my loved ones, and, with the notion that any day truly can be our last, the refusal to wait to say, do, or try anything tomorrow that can be done today.
Helaina Hovitz is the author of the memoir "After 9/11" and works as a journalist and editor focusing on social good, health, and wellness. Follow her work at HelainaHovitz.com and on Twitter and Facebook. She still lives in New York City.