For at least a century, psychologists have assumed that terrible events — such as having a loved one die or becoming the victim of a violent crime — must have a powerful, devastating and enduring impact on those who experience them. This assumption has been so deeply embedded in our conventional wisdom that people who don’t have dire reactions to such events are sometimes told that they have a pathological condition known as “absent grief”. But recent research suggests that rather than being the fragile flowers that psychologists have made us out to be, most people are resilient in the face of trauma.

The loss of a parent or spouse is usually sad and often tragic. But while most bereaved people are sad for a while, very few become chronically depressed. Although more than half the people in the US will experience a trauma such as rape, physical assault or natural disaster in their lifetimes, only a small fraction will ever develop any post-traumatic pathology or require professional assistance.

Indeed, studies of those who survive major traumas suggest that the vast majority do well, and that a significant portion claim that their lives were enhanced by the experience.

Negative events do affect us, but not as much or for as long as we expect them to. When people are asked how they’ll feel if they lose a job or a romantic partner, they consistently overestimate how awful they’ll feel and for how long they’ll feel awful.

If heartbreaks and calamities can be blessings in disguise, then why are their disguises so convincing? The answer is that the human mind tends to exploit ambiguity — and if that phrase seems ambiguous to you, then just keep reading.

In Voltaire’s classic novel Candide, Dr Pangloss is a teacher of “metaphysico-theologo-cosmolo-nigology” who believes that he lives in the best of all possible worlds.

“It is clear,” he said, “that things cannot be other than the way they are; for as all things have been created for some end, they must necessarily be created for the best end. For instance, noses were made to support spectacles, hence we wear spectacles . . . Those who say that everything is well are speaking foolishly; they should say that everything is best.”

Research suggests that human beings are hopelessly Panglossian; we are unusually inventive when it comes to finding the best of all possible ways. And yet, if this is true, then why aren’t we all walking around with wide eyes and loopy grins, thanking God for the wonder of haemorrhoids and the miracle of in-laws? Because the mind may be gullible, but it ain’t no patsy. Our experience of the world — how we see it, remember it and imagine it — is a mixture of stark reality and comforting illusion. We can’t spare either. If we were to experience the world as it is, we’d be too depressed to get out of bed, but if we were to experience the world as we want it to be, we’d be too deluded to find our slippers.

Rather than thinking of people as Panglossian, then, we might think of them as having a psychological immune system that defends the mind against unhappiness in the way that the physical immune system defends the body against illness. This metaphor is appropriate. If the physical immune system fails we are stricken with infections, but if it mistakenly defends the body against itself we are stricken with autoimmune disease. A healthy physical immune system must find a way to defend us well — but not too well.

Analogously, when we face the pain of rejection, loss, misfortune and failure, the psychological immune system must not defend us too well (“I’m perfect and everyone is against me”) and must not fail to defend us well enough (“I’m a loser and I ought to be dead”). A healthy psychological immune system allows us to feel good enough to cope with our situation but bad enough to do something about it. To maintain the delicate balance between reality and illusion, we seek positive views of our experience, but we allow ourselves to embrace those views only when they seem credible.

How do we achieve this? How do we manage to think of ourselves as great drivers, talented lovers and brilliant chefs when the facts of our lives include a pathetic parade of dented cars, disappointed partners and deflated soufflés? The answer is simple: we cook the facts.

To my knowledge, no one has ever done a study of people who have been left standing at the altar. But I’m willing to bet that if you rounded up a sample of almost-brides and grooms and asked them whether they would describe the incident as “the worst thing that ever happened to me”, or “the best thing that ever happened to me”, more would endorse the latter. And I’ll also bet that if you asked a sample of people who’d never been through this experience to predict which of all their possible future experiences they are most likely to look back on as “the best thing that ever happened”, not one of them will list “getting jilted”. Like many things, getting jilted is more painful in prospect and more rosy in retrospect. When we contemplate being hurt this way, we naturally generate the most dreadful view of the experience; but once we have been heartbroken and humiliated, our brains begin shopping for a less dreadful view — and the human brain is one smart shopper. However, because our brains do their shopping unconsciously, we tend to assume that the dreadful view we have when we look forward to the event is the dreadful view we’ll have when we look back on it. We do not realise that our views will change because we are unaware of the processes that change them.