Trading is only a science after you have a large number of trades to put through analysis. At the end of the analysis, you will have a quantifiable set of numbers that states your success/failure.
However, like any statistical analysis, a single trade or small sub-group of trades can have a huge swing in probabilities and may not reflect the true mean average
The funny this is that I was discussing this with the traders in the office and we at first said this only applied to traders with a consistent strategy they did not deviate from. However, we realized that even a trader who was "shooting from the hip" would actually end up doing alot of the same things over and over again and end up with a quantifiable set up numbers that showed the true success/failure of the "system"