You look for the key you are holding in your hand. You walk into a room and stop because you do not know why you came in. You read the page twice and nothing stayed. The first thought is always the same - my memory is failing.

Most likely it is not. Psychiatrist Marian Rojas Estape explains it in one sentence: "If a person lives in a state of constant alert, they spend their mental battery on survival, not on learning and remembering."

What "mental battery" means

There is no battery in the brain; it is a metaphor for limited cognitive resources - above all attention. The prefrontal cortex handles attention, problem-solving and impulse control, and those capacities do not stay unchanged all day. When a large share of attention is permanently occupied by worries, the brain reads that as a threat and prioritises safety. Everything else gets less.

Here is the point usually missed: you did not forget - you never paid enough attention for anything to be recorded in the first place.

Which part of memory suffers

Valeria Medina, a neuropsychologist at NeuronUp, says the most vulnerable is episodic memory - the kind that lets you recall a personal experience together with its place and time. The hippocampus is key: it binds people, places, sequence and emotion into one coherent memory, and for that it also needs the prefrontal cortex to select and connect.

When stress appears, priorities shift. "The release of cortisol and other substances makes the brain prioritise threat detection and rapid reaction," Medina says. Attention narrows onto the danger, and the details get fewer resources.

Hence the contradiction we have all lived: you remember the emotional part vividly, but cannot reconstruct it accurately. "Emotional elements are remembered intensely, but difficulty arises in recalling the place, the time or the sequence of the facts," she explains. Some memories feel incomplete or fragmented - not erased, but partially recorded or temporarily hard to access.

Why this is worth knowing

Because the diagnosis we give ourselves is usually wrong, and usually more frightening than the truth. Someone who has lived under pressure for six months and starts forgetting easily concludes something is wrong with their brain. In the vast majority of cases, the brain is working exactly as it was built to work - spending its resources where it senses danger.

Stress does not break memory. It changes how you attend, build and access memories. The question that follows is a different one from where we started: not what is wrong with my memory, but what has been keeping my alert switched on for so long.