You are speaking of common average strategies which are mediocre strategies at best (below Sharpe 2) . I was talking about very good strategies (above SR 3).Actually I think the truth is more subtle. Strategies that are TA-based, with sound risk management and which work on basic principles do work all the time. But not all the time on every market.
I have seen it many times in forex that a great strategy flat-lines or goes into loss on a pair for no chart-visible reason, while it simultaneously starts to perform well on another pair. It's the most frightening thing in trading.
