My mom used to say that courage lies in every man and woman's heart—and that one day, it will be summoned.

Eighteen years ago this morning, that courage was summoned in response to a horrific act of terrorism that filled clear blue September skies with ash, searing the soul of every American.

Courage was summoned in the hearts of our first responders who answered the call, running into the smoke, rubble, and wreckage.

It was summoned in the hearts of tens of thousands of bystanders—from downtown New York City to the Pentagon to Shanksville, Pennsylvania—who helped save the lives of thousands.

And it was summoned in the hearts of millions of Americans who stood together, united against hate.

It's a basic American instinct to respond to crises when our help is needed—to comfort the afflicted. We have seen it again and again in our darkest hours. It’s an instinct that echoes through our history—from Pearl Harbor to Beirut; from Mogadishu to Ground Zero.

And the true legacy of September 11th is that it ultimately left our spirit mightier, the bonds that unite us thicker, and our resolve firmer.

Today, 18 years later, that legacy is ours to uphold. Every day presents us with a fresh opportunity to remember exactly who we are:

A nation of honesty. Decency. Dignity. Respect. Giving everyone a fair shot, and leaving no one behind. Giving hate no safe harbor.

Choosing hope over fear, and truth over lies. This is America.

Today, we remember. We recommit. And, as ever, we rebuild. Because courage lies deep and beats loud in the heart of every American. Don't forget it.

May God bless America, and may God protect our troops.

- Joe