Revenge trading: after a loss, the brain demands it back immediately, so it upsizes a bad idea. The rule: after two consecutive losses — a twenty-minute break. After three — the day is over.

Endowment and stop-widening: once you own it, you stop analysing the stock and start defending your decision. That's how a widened stop is born. The rule: the stop is set before entry and never moves back.

Sunk cost: holding a loser because "I've already put so much into it". Money already lost is irrelevant to whether this is the best position for your money today. The rule: ask each morning whether you'd buy it now at this price.

Exiting early: fear of losing a small gain takes you out of the trades that were supposed to carry the year. The rule: a partial exit by fixed rule, and a remainder left to a trailing stop.

Overconfidence after a streak: three winners in a row create the sense that you're reading the market, and immediately after comes a double-size position. The rule: size comes from the calculation, not from mood.

Confirmation bias: once you own it, you only read what agrees. The rule: before entering, write down explicitly what would prove you wrong — the third line from the thesis lesson.

Fear of missing out: buying after the stock has already run 40%, because everyone is talking about it. That's precisely the point of highest risk and lowest remaining upside. The rule: enter only on a defined setup with a defined stop — if the level is already behind you, there's no trade.

And the rule that covers them all: every rule is written in advance, in a calm moment, not invented in real time. In real time the brain can justify anything, so there's no point arguing with it — you simply read what you wrote earlier.