The "big mistake" in Forex trading can refer to a number of different things, but one common mistake that many traders make is failing to implement a disciplined approach to risk management. This can take many forms, such as failing to set stop loss orders, overleveraging trades, or taking on excessive risk. Another common mistake is allowing emotions to drive trading decisions, such as getting too attached to a particular trade or failing to cut losses when they become too large. Finally, traders may also make the mistake of failing to adapt their trading strategy to changing market conditions, such as when volatility increases or when new economic data is released. By being aware of these common mistakes and taking steps to avoid them, traders can increase their chances of success in the Forex market. This can include investing in education, developing a strong trading plan, and approaching trading with discipline and a long-term perspective.