This essay is part of How to Live With Regret, a series exploring the nature of regret and the role it plays in all our lives. Read more about the project here.

For most of the last 50 years I have been afflicted with a perverse regret: that I did not die in Chile on Sept. 11, 1973, the day that a military junta overthrew Salvador Allende, our country’s democratically elected president.

Entranced by Allende’s project to attain socialism without resorting to violence — perhaps a first in world history — I went to work for him in the presidential palace, La Moneda. Besides advising Allende’s chief of staff on cultural and press issues, my duties included sleeping one night each week on watch duty at La Moneda. If I had kept to the pre-established rotation — I was scheduled for the night of Monday, Sept. 10 — I would have been present on the morning of the 11th and, in all probability, would have perished, along with Allende and most of his advisers.

But I had asked Claudio Jimeno, an old buddy from university, if I could take his shift on Sunday, Sept. 9, so I could show my 6-year-old son, Rodrigo, the place where I worked. Claudio had gladly accepted in order to spend some time with his own sons, Cristobal, 2, and Diego, 1.

So it had been Claudio, and not me, who had been alerted on that Tuesday dawn that the military was seizing power, Claudio who had resisted as the building was being demolished by tanks and bombs, Claudio who had been captured by troops and then tortured and executed, Claudio whose body had been disposed of anonymously, never returned to his family for burial.

Those images haunted me during the interminable years of exile and through my many returns to dictatorial Chile. The one that I kept picturing from that day was of Claudio by Allende’s side, Claudio who had been loyal to the president to the very end.