As you sat across the Thanksgiving table basking in the warmth of family and the aroma of chestnut stuffing, most likely you did not remember the vicious comment your Aunt Jennifer made about you a few years back. You didn't dwell on Uncle Julio's unkind reference to your drinking last Christmas or what cousin Duwan said about your girlfriend during that dreadful vacation at the shore. At family holidays, we tend to embrace our relatives even after months or years of not having seen one another, regardless of the quarrels we have had in the past.

We may chalk up our generous forgiveness to the festive spirit of the holiday, but the real reason has nothing to do with Thanksgiving. It is because of how we humans remember - and forget. Cognitive experts tell us that forgetting is fundamental to how we make sense of the world. Forgetting helps us survive, by making sure we don't dwell in the past.

In the digital age, that mechanism of our humanity is under threat.

We all hate when we can't remember something. We think of it as a bug of the human mind. We don't realize that by discarding most of the avalanche of details that our senses are bombarded with every day, as well as past wounds, our brain helps us focus on the important things. It lets us see the forest rather than just the trees. We may learn from our failures, but thankfully we also easily forget them.

Human memories are not fixed, they are reconstructed. We remember more easily what we remember often. More important, we tend to forget memories that don't fit into our current world vision. Our brains discard them as no longer important. That way, we forgive one another (and ourselves) for past transgressions. Thus our memories of most past experiences wither. Of course, that process takes years, as more and more details dwindle in our minds.

Forgetting misdeeds that we deem no longer relevant is a powerful mechanism; and it is built into us. We don't have to do anything consciously to make it happen. But that operation is thwarted in a world of comprehensive memory in which we are constantly reminded of our past.

Our ever-improving digital tools record billions of Facebook messages and more than 300,000,000 tweets every day - not to mention our private email accounts, with their photos and videos. Logging our lives is becoming the norm, and having a comprehensive digital memory at our disposal is the default.

Many people are concerned about what this does to privacy. I am worried about Thanksgiving - the warmth and joy that may be lost when we keep being reminded of every mistake or disagreement.

Imagine that some years back, Jane was accused by her cousin John of neglecting a sick family member. The accusation wasn't entirely fair; Jane had gotten caught in traffic and her ill aunt was alone for an hour. John sent her a nasty email. The email infuriated Jane, but as time passed the memory of the incident faded and more recent and pleasant memories replaced the bad one. But suppose, while searching for driving directions to this year's family gathering, Jane stumbles over John's email just as she is about to see him. With her anger revived by rereading the old message, will she be able to face him without the recalled memory biasing her judgment?

With comprehensive digital memories all around us, forgetting one another's offenses becomes more difficult; through our digital tools we'll be alerted to all that we thought we had forgotten. This will make it harder for us to forgive.

In one of his short stories, the Argentine author Jorge Luis Borges describes a young man who after an accident can no longer forget. He can remember perfectly all the books he has read, but cannot learn anything from them, because learning involves the distilling of abstract thought from detailed memories, after which the latter fade away. Thus it, too, necessitates forgetting.

We need to appreciate and preserve forgetting as a feature of humanity. To do so may require us to adapt our digital tools. Unlike our brains, they can easily be rewired. With the help of the companies that design our online tools, we could let tweets and Facebook comments expire over time. We could choose the photos and emails we want to remember, as we let the rest slowly disappear; thus giving us a renewed and much-needed chance to forget.

This would preserve our ability to grow, learn and forgive. And it would give us a better shot at having a rancor-free family holiday. That alone would be worth it.

Viktor Mayer-Schonberger, the author of "Delete: The Virtue of Forgetting in the Digital Age," is a professor of Internet governance and regulation at the Oxford Internet Institute. He wrote this for the Washington Post.