Emotions are the most easily overlooked cost. Many people talk about trading, focusing only on technical indicators, patterns, and logic, but rarely do they seriously confront emotional issues. For me, what truly causes my account to fluctuate is never the market, but emotions. When I am consecutively profitable, I unconsciously relax discipline, increase position sizes, and chase prices, thinking "I'm in good shape." When I experience consecutive losses, I rush to recover, trade frequently, and end up making things worse. Later, I gradually realized that emotions themselves are part of trading costs, and they are the hardest to quantify yet the most deadly. My current approach is simple: once I have two consecutive losing trades, I will force myself to stop trading. If my emotions are noticeably unstable that day, for example, due to distraction from other matters, I simply refrain from trading. Trading is not just analyzing the market; it’s also managing oneself. When emotions are stable, strategies are meaningful; when emotions are out of control, even the best strategies will distort.