I will never forget where I was when three world events occurred: the terrorist attacks of Sept. 11, the death of Pope John Paul II and the recent tragic plane crash in Smolensk, Russia.

On April 10, Poland’s President Lech Kaczynski and almost 90 other dignitaries – among them prominent members of parliament, war veterans, generals and priests – traveled to Smolensk, Russia, to celebrate the 70th anniversary of the Katyn massacre of 22,000 Polish POWs by the Soviet union. The plane crashed, killing them all.

I have both an American and a Polish passport. I spent my entire life living in the U.S. and visiting Poland almost every summer.

News of the plane crash resonated with me. I met Arkadiusz Rybicki, a member of Poland’s parliament who perished in the crash, at a seminar last summer.

My senior thesis was about the Katyn massacre of 1940, which the dignitaries who perished in the plane crash had traveled to Russia to commemorate.

I was never a fan of Poland’s late President Lech Kaczynski, one of the 96 victims of the crash. I felt alienated by his confrontational style of politics and his support for the expansion of government spending.

Yet Kaczynski’s death made me feel guilty for the times I criticized him, sometimes perhaps too harshly. Despite my ideological differences with Kaczynski, I now have no doubts he was an authentic Polish patriot.

Kaczynski defended Georgia against Russian imperialism more vocally than perhaps any other European leader.

Since last week, Polish streets and churches have been full of people crying, praying, waving flags and lighting candles.

Many great historical figures died in the plane crash. Among them was Anna Walentynowicz, sometimes called “the Polish Rosa Parks.” She was a crane operator whose refusal to be fired from the Gdansk Lenin Shipyards in 1980 inspired the first strikes that led to the formation of Solidarity, the 10 million member labor union that restored democracy in Poland in 1989.

This reminds me of what occurred five years ago, when John Paul II died. Poles everywhere became more charitable and more forgiving. This wasn’t only a tragic loss for the Catholic Church, as evidenced by the outpouring of grief from Poland’s Jewish, Orthodox and Protestant faithful, as well as many non-believers.

When I was 13, I discovered that living in a prosperous democracy with the world’s most powerful military isn’t enough to guarantee safety. The terrible tragedy of Sept. 11, 2001, proved to me just how vulnerable we are.

Like the Poles in 2005 and 2010, millions of Americans stormed their churches, put flags in their windows and donated extraordinary sums of money to the families of the victims of al-Qaeda’s repulsive crime.

I also remember many beautiful gestures of solidarity in the aftermath of the Columbine massacre.

Poles, Americans and people of all nations become more human when they experience great collective suffering. People feel guilty about their lack of love for others, and feel helpless.

And we should feel weak. The terrorist attacks of Sept. 11 and the plane crash in Smolensk prove to us that humans are not invincible. We can die at any moment.

And so can our neighbors. Every time we yell at our coworker, have a petty fight with a family member and ignore the suffering of others we should feel great shame, for those close to us might not be there the next day.

In a few weeks, everything in Poland will be back to normal. The candles and photographs of President Kaczynski will disappear, just as a few months after Sept. 11 when fewer Americans displayed their flags in their yards, and the same garbage that’s normally on TV replaced the beautiful charity concerts.

I hope this tragedy will be a reminder to live as if this were my neighbor’s last day.