Patti Davis is the author of the new novel “The Wrong Side of Night” and is the daughter of Ronald and Nancy Reagan.

Sad anniversaries collapse time. No matter how many years have passed, when the day arrives you are back there again. You remember the slant of the sun, how time seemed to lumber and stall; you remember smells and images and voices telling you things you never wanted to hear.

“There’s been a shooting,” one of my Secret Service agents said. His face seemed drained of blood.

He had burst into my therapy appointment. When he opened the door, my first reaction was anger — how could he just intrude on a session like that? But then I saw his face and heard words I would never forget.

At first, we thought that Jim Brady had been killed — everyone did. Slowly, over what seemed like hours but probably wasn’t, the news became consistent and mostly accurate: My father was in surgery, Brady and two other men had also been wounded; Brady had been shot in the head.

The Secret Service wouldn’t allow any family members to get on a commercial flight; they had to assume the worst, that maybe all of us were targets, maybe John W. Hinckley Jr. wasn’t acting alone. At the end of the day, Michael, Maureen and I boarded an Air Force transport plane and got to Washington long after midnight. Ron was flown in from somewhere in the Midwest. We still didn’t know whether our father would live.

I remember that flight as though it happened last week — the noise of the plane, the uniformed soldiers, the white-bread sandwiches they gave us though no one was very hungry. And the fear — it rode along with us as we flew across the country into night.

Shock is a strange thing — it crystallizes some memories and blurs others. I can still see my mother sitting up in bed clutching a shirt of my father’s — she’d held onto it all night, breathing in his scent. I don’t remember the drive to the hospital, but I remember coming into the room and seeing my father. His face was so pale it was almost translucent, and I had the sudden feeling that he might have died and come back.

There is a broader memory that has stayed with me through all these decades. It settled into me, like water finding its own level. It’s the memory of how this country felt in the days and weeks after my father was shot. Politics suddenly became incidental, almost irrelevant. The president and three other men had been brutally gunned down. People were stunned, grieving, softened by sadness. Strangers opened their arms to me, and I gratefully accepted their embraces. I felt it everywhere — people bonded by sympathy and compassion, by a feeling that an attempted assassination inflicted a wound on the entire country. There was no room for divisiveness, for the hard-drawn lines of political differences.

I touch the edges of that memory now and a deeper grief is ushered in. Because I don’t know whether we will ever experience that shared sympathy again in the United States. The lines have cut too deep, the distances are too great, and cruelty has become mainstream. We have put down roots in soil that doesn’t nourish us, but rather poisons us. And I don’t know whether any event or tragedy will compel us to replant ourselves in healthier soil.

But it is worth remembering that, for a while, a long time ago, that’s who we were. Maybe just for a few weeks or months, but we knew how to get there. Somewhere in us there is a cellular memory of being a people who turn away from vicious name-calling, who dismiss political differences and who simply care about one another.

The poet Rumi wrote: “Out beyond ideas of wrongdoing and rightdoing, there is a field. I’ll meet you there.” On the horrible day that my father and three other men were shot, we as a country found that field and went there to heal. My hope is that we never face another assassination attempt. But my hope is also that we learn to believe that field is still there, and that we choose to find it.

Read more: