My mother told me that as a child I would occasionally steal into my older brother’s room and vandalize some architectural project he had spent weeks working on in his uncommonly meticulous fashion.

I don’t know why I did that. In fact, I don’t remember doing it. But according to my mother, my brother would simply say, “It’s all right. I was done with it anyway.” And she, astonished, would think to herself, “This cannot be my child.”

I was reminded of this in the aftermath of a recent incident at the Asian Art Museum in San Francisco, which provided me with a lesson in the emotional physics of violence, in the terrible ease with which the sense of being violated can escalate into a never-ending ping-pong of vengeance. It was also a study in the power of a solitary act of forgiveness.

I went to the museum to see an exhibit called “Wisdom and Compassion: The Sacred Art of Tibet.” A group of monks from the monastery of the Dalai Lama were creating a six-foot-wide mandala — a sort of spiritual rendering of the cosmos — made of colored sand ground from gemstones.

For nearly a month, they worked silently, bent over the low platform which cradled the growing sacrament. They laid out their intricate geometry of devotion by hand, surrounded constantly by onlookers who stood sometimes for hours, as I did, simply watching, our busy lives uncharacteristically forgotten.

Although the mandala didn’t fit my taste in art, I was absorbed by the artistry and concentration that went into it. I was also astonished that anyone could stoop for so long without complaint. But the greatest measure of the project’s drama and poignancy was that it was temporary. In the Buddhist tradition of nonattachment, the monks intended from the very start to dismantle their creation after a few months on exhibit, and scatter its remains in the sea.

All that work wasted, I thought to myself.

The day before the mandala’s completion, just as the monks were putting the finishing touches on it, a woman jumped over the velvet ropes, climbed onto the platform, and trampled it with her feet, screaming something about “Buddhist death squads.”

It was as shocking as it was inconceivable, a desecration not unlike wiping your backside on the Shroud of Turin, and an awful and profane misunderstanding of someone else’s intentions. When I read about it in the newspaper the morning after, my head filled with images of vengeance and rightful punishment.

But when I reached the end of the article, my rage turned into disbelief. In stark contrast to my own response, the monks’ was one of exoneration. “We don’t feel any anger,” said one. “We don’t know how to judge her motivations. We are praying for her for love and compassion.”

They might as well have said, “It’s all right. We were done with it anyway.”

Sitting in my kitchen, I felt as astonished as my mother once had. Coming from a long line of avengers — people who have demanded eyes for eyes and teeth for teeth — I’ve always had a difficult time with forgiveness. I have hung on to certain betrayals all my life, refusing to let go of things I long ago lost forever.

Still, when I heard that the museum officials were considering pressing charges against the marauder, it seemed this would almost dishonor the monks’ gesture of absolution — an act which had greatly defused the situation, drained much of the bitterness from it, and set a very hard example to follow.

I have taken a critical look at my own reaction, at the awful instinctiveness of it, and at the alternative provided by the men who should have been the most outraged, but weren’t. I understand that I am moved by this incident precisely because I saw the mandala and the monks with my own eyes; perhaps I would find forgiveness more quickly if I saw this woman for myself, bathed myself in her presence just as I did in the mandala’s, wondered how many grains of sand she is made of, and who it was who worked on her.

The real teaching of the mandala has turned out to be not in its execution but in its . . . execution, its demise, and in how its creators responded to its death. Once again, life has imitated art: we know it’s going to end, but it’s still shocking sometimes how it ends, and how little any of it turns out the way we had intended. The grace is in how we respond to the challenges which fate puts in our way to test our resolve.

The monks have reminded me that to forgive is indeed divine, but that ordinary people can do it. Although I will admit that revenge can be unmistakably sweet, I also believe that the succor of revenge is no competition for that of forgiveness — not in the long run. It’s well and good to have laws that punish wrongdoing, but they can’t set your soul to rights after you’ve been wronged. This is the hard, human work — although the monks showed us there is a kind of divine contagion to even a single act of amnesty.

What is, for me, permanent about this impermanent exhibit is that I will take with me a few grains of the wisdom and compassion that were demonstrated there. I will honor the monks’ message all the more adamantly for knowing how the mandala was destroyed. And the woman, under psychiatric supervision somewhere, turns out to have been a great teacher.