When I think about my first year in Vietnam, I think about a morning on a small balcony, a cup of black coffee, the heat rising before the city was properly awake. Motorbike horns somewhere down the lane. The smell of a pho restaurant a few doors over. Everything new, everything mine.

That’s what I remember. What I am not remembering, or what comes back only when I try, is the loneliness of the first few months. The visa stress. The phone calls home that left me flat. The number of evenings I sat alone in a stranger’s city wondering what I’d done to my life.

Both were real, but only one made it into the highlight reel.

This is not just a quirk of mine. In the 1990s, researchers Terence Mitchell, Leigh Thompson and colleagues asked people to rate three meaningful experiences — a Thanksgiving vacation, a trip to Europe, a three-week cycling tour — before, during, and after the event.They reported that “people’s expectations of personal events are more positive than their actual experience during the event itself, and their subsequent recollection of that event is more positive than the actual experience.” Most of us seem to remember such moments as better than they actually were. 

I notice the same edit when I think back to university in Dublin. What comes up first is the freedom of it. Walking back across the city at one in the morning. The slow afternoons in a small student apartment. What doesn’t come up are the less pleasant experiences; the exam dread, being  broke and routinely not knowing what I was going to do with my life. Those years were good, but they were also a lot of other things. The memory has decided which of those it is going to carry forward.

The same edit again, further back. My childhood — the long unstructured summers, the be-home-by-dark rules, the freedom my parents handed me — registers now as bucolic. It probably wasn’t, all the way through. Boredom was the default state. Whole afternoons stretched out with nothing in them. I remember it as light; at the time it was often heavy. Memory has gone in afterwards with a soft brush and cleaned it up.

There is a likely a second effect at work here, and it explains a lot. Psychologists W. Richard Walker and John Skowronski call it the fading affect bias. Their 2009 review puts it plainly: “the intensity of affect associated with negative autobiographical memories fades faster than affect associated with positive autobiographical memories.” The bad stuff doesn’t disappear from the record — it just loses its edge faster than the good stuff does. So over a few years, on its own, with no help from you, the past tilts sunny. They argue this is not an accident. The softening seems to be doing something for us; their suggestion is that it may help “induce individuals to be positive and action-oriented” so we can face what’s in front of us.

In other words, memory’s softening looks more like a feature than a bug.

If we walked around carrying the full weight of every dull afternoon, every visa worry, every two-a.m. existential moment in someone else’s city — at full original resolution, every time we looked back — the past would be unlivable to revisit. Many of us would not sign up for any of it twice. The softening is what makes a life feel coherent when you look at it from a distance. It is, in a quiet way, one of the kindest things our wiring does for us.

At the University of Southampton, the psychologist Constantine Sedikides and his colleagues have done some work on nostalgia. They frame the warm version of memory as a kind of psychological resource — one that “fosters self-continuity by augmenting social connectedness.” In plain English, the soft past is one of the things that lets you feel like you are still you. The thread between Vietnam-me, Dublin-me, kid-me and the man typing this is partly held together by the fact that those earlier versions are remembered with a little extra light.

So there is no point being annoyed at the rear-view mirror for the rose tint. It is there for a reason.

The thing worth being careful about is what the rose tint can talk you into — moving backwards. Trying to recreate the chapter the way you remember it, rather than the way it was. The trap is not fond memory; the trap, I think, is treating fond memory as a map. The first year in Vietnam was a real first year, and it was a great one, but it was also harder than the balcony shot I default to. If I went back trying to find that exact morning, I would end up disappointed. The morning is gone, and the version I keep is the only version I get.

That, I think, is what the old line about the good old days is really getting at. They look that way because something has been quietly cleaning them up while we were not looking. The kindness wasn’t there at the time — it is the part the years added on the way out.