Certain kinds of thinking cost more than others. Mentally returning to a past moment — really returning, not just glancing — requires the mind to reconstruct something that no longer exists. The room, the light, the particular quality of a voice. When that moment carries emotional weight, the reconstruction doesn't stay intellectual. The body enters it too. Heart rate shifts. Breathing changes. The nervous system begins responding to something that isn't happening.

This is expensive.

I don't mean expensive in some vague, moralising way. Psychologists have a term for this pattern: rumination. The word comes from the digestive process of cows — chewing the same material over and over. When applied to thought, it describes the repetitive focus on distressing content without movement toward resolution. Research published in Stress and Health this year found that people who score high on rumination measures show exaggerated cardiovascular responses to stress and, critically, slower recovery afterward. The body stays activated longer. It doesn't settle.

There's a difference between remembering and dwelling that took me years to understand. Remembering can be reflective, even nourishing — a way of honouring what happened, integrating it, letting it inform the present without dominating it. Dwelling is something else. Dwelling is immersive, comparative, and repetitive. It doesn't integrate. It displaces. The present gets evaluated not on its own terms but against a version of the past that has been retrospectively polished until it gleams.

That comparison is unwinnable.

The past you're measuring against isn't even accurate anymore. Memory doesn't archive experience faithfully. Every recollection is a reconstruction — and reconstruction favours emotional intensity over factual precision. A period that was actually mixed, containing both good and difficult moments, can crystallise into pure golden light when viewed from sufficient distance. The mundane parts drop away. What remains is the atmosphere, stripped of its complications. You end up competing with a ghost that never existed.

A study from the University of Liverpool identified dwelling on negative events as the single biggest predictor of both depression and anxiety. Not the events themselves — the dwelling. The cognitive pattern of returning again and again, generating alternatives that cannot be pursued, asking questions that cannot be answered. What if I had stayed? What if I had said something different? The brain is remarkably good at generating counterfactuals. It is remarkably bad at closing them when the alternatives are impossible. The loop has no exit.

I've been writing about memory for a while now, trying to understand why certain fragments refuse to stay in the past. Part of the answer, I think, is that emotionally vivid memories don't behave like dated entries in a calendar. They feel concurrent with the present. They resist being filed under "then." When I dwell on such a memory, I'm not looking backward at a fixed point. I'm experiencing something that seems to exist alongside now, competing for the same attention, drawing from the same limited pool of emotional energy.

And that pool is limited. Attention, once fixed, is expensive to keep fixed. Emotion that has nowhere to go — no corrective action, no completion, no resolution — exhausts rather than motivates. This is one reason beautiful memories can leave a person feeling depleted afterward. The emotion is real. The activation is real. But there's nothing to do with it. No way to act. The feeling cycles without discharge.

I should say plainly: I don't think any of this means the past should be ignored or that reflecting on difficult memories is inherently harmful. The problem isn't memory. The problem is a specific relationship to memory — one characterised by repetition without integration, by comparison without acceptance, by emotion without agency. The psychological literature calls this "brooding" as opposed to "reflective pondering." Brooding predicts worse outcomes. Reflective pondering can actually help.

The distinction is subtle but feels obvious once you notice it. Reflective pondering asks what happened and what it means. Brooding asks why this happened to me and whether it could have been different. One moves toward understanding. The other moves toward a wall.

Some of the fatigue, I suspect, comes from temporal misallocation of meaning. When a specific period of the past comes to carry disproportionate emotional weight, the present is quietly stripped of legitimacy. New experiences feel thin because they're not allowed to matter in the same way. They're measured against something that has been idealised through distance and repetition. Even neutral or potentially good moments struggle to register because attention has been monopolised elsewhere.

I notice this in myself. There are stretches of time when my present life is fine — genuinely fine, not pretending — but a certain flavour of memory keeps surfacing, and each surfacing takes something. Not much. But accumulating. Like a tax on attention. After a day of this, I'm tired in a way that doesn't correspond to what I've actually done. The body knows it has been working even if the work is invisible.

Recent research in Frontiers in Psychology found that fatigue itself can trigger rumination, creating a feedback loop. Tired people dwell more. Dwelling makes people tired. The cycle reinforces itself. Breaking out requires noticing the pattern — recognising when remembering stops adding depth and starts extracting vitality. That recognition doesn't fix anything by itself, but it marks the point where awareness begins to replace compulsion.

Self-compassion appears to help. Not in the sense of empty reassurance, but in the sense of treating yourself with the same patience you'd offer someone else caught in the same loop. A study published in Nature this year found that self-compassion mediates the relationship between self-critical rumination and anxiety. Which is to say: how you relate to the pattern matters as much as the pattern itself. Beating yourself up for dwelling only adds another layer to the thing you're dwelling on.

I'm not sure I've gotten better at this. I've gotten better at noticing it, which is something. When I catch myself returning to the same moment for the third or fourth time in a day, I can sometimes name what's happening: reconstruction is active, the body is responding to something that isn't here, energy is being spent on a comparison I cannot win. Naming it doesn't stop it. But naming it creates a small gap between the experience and my identification with it.

The hard part — the honest part — is accepting that some memories will keep arriving whether I want them to or not. They'll bring their weather with them. The question isn't how to make them stop. The question is whether I let them run the whole day or whether I can acknowledge their arrival and then, with effort, redirect attention to something I can actually affect.

Some days I manage. Some days I don't.

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