Many traders cannot trust their own systems or strategies because the sample size they are looking at is too small.

The sample size they tested beforehand is also small, and, what's more, the point at which they decide "this doesn't work" in live trading is likewise far too early.

In other words.

① They start with large confidence gained from an unreliable small sample-size test.

② They use the results of an unreliable small sample-size live trade.

③ They keep making unreliable decisions.

What needs to be large is the sample size.

Unless you shift to a long-term perspective and the sample size you monitor becomes large, no strategy will lead you to success.