Firefighters raising an American flag from the rubble. Ordinary civilians joining rescue workers to search for survivors. Democrats and Republicans singing “God Bless America” together on the steps of the U.S. Capitol.

If you aren’t old enough to remember the aftermath of 9/11, it might seem hard to believe how our country came together after it was attacked. It did happen, however, and to many, those days and weeks still seem like yesterday.

The overriding focus on every 9/11 anniversary should be praying for the victims and their families. Nearly 3,000 Americans were murdered by al-Qaeda terrorists on that terrible day, and our utmost priority must always be making sure that those innocent people are never forgotten. My family will be paying our respects next week at the National September 11 Memorial & Museum in New York, which I urge everyone to visit.

We must also remember the thousands of firefighters, police officers, rescue workers, intelligence officers and U.S. troops who made the ultimate sacrifice in the 21 years since 9/11. While most Americans eventually went back to their daily lives, a selfless group of America’s best and bravest kept stepping forward to serve long after the fires were put out at the World Trade Center, Pentagon and a Pennsylvania field. I have written about some of these American heroes, and it always inspires me how long after 9/11, they never stopped fighting.

I am currently writing a book about fallen U.S. Army Staff Sgt. Michael Ollis. He was only 13 years old on September 11, 2001, but immediately felt the impact of the attacks. He grew up in Staten Island, just a short ferry ride from the World Trade Center. Some of his closest relatives were in Manhattan at the time of the attacks and several neighbors and family friends lost loved ones in the Twin Towers that day.

Michael already had his eye on a military career before 9/11, but after that tragic day, he decided to devote the next four years of his life to preparing to be a soldier. On his 17th birthday, with his parents’ permission, he enlisted in the U.S. Army.

From age 17 to 24, Michael deployed three times: once to Iraq and twice to Afghanistan. He made the ultimate sacrifice on August 28, 2013, while saving the life of a Polish soldier during a major terrorist attack on their base.

While sorting through Michael’s writings and personal belongings over the past few months, I’ve found everything from journal entries and drawings to poems focused on 9/11.

“I see the terror that hurts the city,” Michael wrote in his high school journal. “I hear the screams from the towers.”

The soldier from New York, who was posthumously awarded the Distinguished Service Cross for heroism displayed in Afghanistan, wasn’t overseas fighting for himself. He was honoring the victims of 9/11 by defending the defenseless.

Next week, I will be joining the Ollis family for a baseball game being played in honor of Michael on what would have been his 34th birthday. Having spent his entire adult life training and deploying around the world, he never got a chance to marry or have children. Like thousands of fellow American heroes since 9/11, Staff Sgt. Michael Ollis sacrificed his tomorrows for our todays.

Just steps from where that baseball game will be played stands Staten Island’s 9/11 Memorial, which I first got a chance to visit in July. With the Freedom Tower soaring just across the Upper New York bay, the monument honors 263 Staten Island victims of 9/11 and the 1993 World Trade Center bombing. A separate memorial honors first responders who lost their lives in the years since 9/11 from exposure to toxic fumes.

What struck me most about the memorial was that every 9/11 and 1993 victim’s plaque includes their meticulously carved silhouette. It’s a beautiful and haunting tribute that must have taken an incredible amount of work to accurately depict. It’s also a stark reminder that the victims of both terrorist attacks were real people with unique stories and countless loved ones still grieving their loss.

I hope Americans can someday reunite like we did in those first months after 9/11. What happened 21 years ago was a tragedy of historic proportions, but also a reminder that at the end of the day, we are all on the same team.

Tom Sileo is a contributing senior editor of The Stream. He is author of the forthcoming Be Bold and co-author of Three Wise Men, Brothers Forever, 8 Seconds of Courage and Fire in My Eyes. Follow Tom on Twitter @TSileo and The Stream at @Streamdotorg.