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Best day / Worst day

These are your two extreme days, measured on the session's cumulative P&L rather than on a single trade. They complete the per-trade extremes: a trader can have no abnormal loss on any trade and a catastrophic day, because they took twelve of them.

The formula

The best and worst cumulative P&L on a single day.

How to read it

Your extreme days. A huge worst day = a day without discipline.

Open your worst day and count the trades. In the large majority of cases there are clearly more than on a normal day, and they cluster after the first loss. That is the signature of revenge trading, and it is exactly what a daily loss limit prevents.

The classic mistake

Taking comfort because the best day offsets the worst. In a prop firm they do not offset: the daily limit is measured day by day, and a single breach closes the account whatever the balance. An average has never saved a challenge.

To go deeper on this : read the full guide. Every term is gathered in the glossary.