Over-Optimisation is one of the most overlooked risks in retail trading. 

Traders try to make their strategies as precise as possible by adding every conceivable parameter. Although this can be advantageous in enhancing historical performance, it also decreases robustness in live market conditions. Fit-to-pattern strategies typically do well only in the time period for which they were built. 

That fragility is costly in forex markets, where conditions change constantly. This constant tweaking is also leading to more emotional involvement and inconsistency. 

By contrast, simpler and better-tested strategies tend to be far more robust when it comes to uncertainty. 

Thus, resilience, not perfection is where true strength lies, making sustainable traders prefer robustness over near term accuracy.