Why does your field of view shrink exactly when you need it widest?

Why this matters. Under load you do not think worse in general. You think about less, and you do not notice the narrowing while it is happening.

One position is moving. Everything else on the screen — the other holdings, the correlation, the thing you meant to check — goes quiet. Not forgotten. Just not present.

Why the narrowing is not a malfunction

It is what attention is for. Under load, a system that focuses on the salient thing is usually right: the loud thing is usually the important thing.

In markets it frequently is not. The loud thing is the position that moved; the important thing may be the exposure you now hold across three correlated positions, which makes no noise at all.

So the mechanism works as designed and the design is wrong for the environment. That is a recurring shape in this domain, and it is why the domain's answers are structural rather than motivational.

What does not work

Deciding to keep the wider view. Narrowing is not a choice being made badly; it is a state, and instructing yourself out of a state is the least reliable move available.

What does

An external list that does not narrow. A checklist read rather than recalled is not subject to your attentional state — that is its entire advantage, and it is why checklists exist in every other high-load profession.

The artefact

A pre-written check, three to five items, kept where you will see it: total exposure, correlated positions, what you said would invalidate this, when you last ate, what you would tell someone else in this position.

Written once when calm. Read, not remembered — remembering is the faculty that is currently compromised.

Try it now

Write your five items now, while nothing is moving. That is the only condition under which the list can be written honestly.