I stood atop Chabad World Headquarters in Brooklyn, N.Y., and watched the sky burn.

It was just two months after I married my wife, Chana, and we were living in Crown Heights, just a half-hour subway ride from Lower Manhattan.

That morning, as I was walking to services, a colleague informed me that if I were to go to the roof of the synagogue, I would see “a fire on the top of the Twin Towers.” It was not long until we learned it wasn’t just a fire, but a terror attack. Standing on the rooftop, I heard the reflection of a fellow standing nearby, “We are experiencing here in America what they constantly experience in Israel.”

Terror hit home.

As we mark 20 years, we reflect on the horrors of that tragic day as well as the triumphs.

We reflect on the things that were taken from us on 9/11: the lives lost, the families broken, the collective pain of our nation and the need for heightened security. We also continue to pray for those today battling 9/11-related illnesses.

We also reflect on the things the terrorists could not take from us: our pride and values. They destroyed towering edifices of steel and concrete, but the foundation upon which our country was built remained intact. They could destroy the tallest buildings, but our moral rectitude stands taller. They cruelly ended thousands of lives, but our commitment to life shines ever brighter.

Kabbalah, Jewish mysticism, teaches that every creation has a counterpart “twin.” Just as there are negative energies, there are positive ones.

How do we combat terror?

Of course, there is the physical and practical avenue: taking security seriously and saluting the courage of law-enforcement agencies in their fight against terror.

And there is the “spiritual twin.” Darkness cannot be countered with more darkness; it can only be dispelled with light. The terrorists sought to break our spirit with an evil we never imagined, and so we need to combat that by uniting with equally unimaginable love.

As we enter the Jewish New Year, let us pray that we all be inscribed in “The Book of Life” with prosperity, mutual respect, tolerance, happiness—and good health to enjoy it.