Why does the trade after a loss look nothing like the trade before it?

Why this matters. The most dangerous position is frequently the one that follows a loss, and its danger has nothing to do with the position itself.

A loss closes. Within minutes the next idea appears, and it is different in ways you would struggle to justify if asked: bigger, or faster, or on a shorter horizon, or in something you do not normally touch.

What changed

Not the market. The account you are mentally keeping. The loss opened a balance that wants closing, and the next position is being asked to do a second job — not just to be a good idea, but to settle the previous one.

Replicated: Thaler and Johnson (1990) documented the break-even effect, where people take risks after a loss they would not take otherwise, specifically to get back to level. The mental account is doing the work, not the arithmetic.

A position asked to do two jobs is sized and timed for the second one.

The part that resists willpower

You can know all of this and still take the position. That is not weakness — the effect does not run through beliefs, so correcting the belief does not correct the behaviour. What has evidence behind it is not a resolution but a prior instruction: if-then, written when nothing was open.

The artefact

A post-loss rule, pre-committed, and short enough to be unambiguous: after a loss of more than X, the next entry waits until the following session. Or: the next entry is at standard size, no exception.

The rule is not there because waiting is virtuous. It is there because it converts an in-the-moment decision — made in exactly the state that distorts it — into one made in advance, and that substitution is the only reliable move this domain has.

Record the exceptions too. A rule with unlogged exceptions is not a rule; it is a preference you have about yourself.

Try it now

Write your post-loss rule in one sentence, in if-then form. Then write, honestly, how many times you would have broken it in the last month.