Definition

Review sequences of losing closed trades.

Formula. Longest consecutive sequence of negative net closed-trade results, ordered by close time and then trade ID. A win or break-even trade resets the sequence.

Expected longest losing run by chance

Approximate expected maxima for independent trades. Real trades are correlated through regime and through your own state, so observed streaks run longer.
Win rateOver 100 tradesOver 500 trades
60%about 5 in a rowabout 7 in a row
50%about 7 in a rowabout 9 in a row
35%about 10 in a rowabout 14 in a row

How it goes wrong

Treating an ordinary streak as a signal
At a 35% win rate, ten consecutive losses is an expected event, not a broken strategy. Size your risk so that the expected streak is survivable and the question stops being urgent.
Ignoring what the streak did to your sizing
The damage is usually not the streak; it is the position size increase that followed it. The journal entries during a streak are the most valuable ones you will ever write.

Questions

How is a streak counted?

The longest consecutive sequence of negative net closed-trade results, ordered by close. A win or a break-even trade resets the sequence.