Losing streak
A run of consecutive losing trades. With a 50% win rate, 6-7 losses in a row over 100 trades is statistically normal; the plan is built around that.
The length of a losing streak depends on the win rate: for a strategy that wins 40% of the time, expect 8-9 losses in a row. Risk per trade is set so that such a streak passes as ordinary fluctuation.
Raising risk during a streak (trying to "win back" losses) is the most common behavior that ends accounts; the right reflex is the opposite: cut size or take a break.