Expectancy = (win rate × average win) − (loss rate × average loss). The result is what you make, on average, per trade. Positive means an edge. Negative means every extra trade walks you toward a loss, no matter how good it feels.

Example: a 40% win rate, average win of 3 units, average loss of 1 unit. Expectancy is 0.4 × 3 − 0.6 × 1, which is 0.6 units per trade. An excellent method — even though most trades lose.

Some methods have a low win rate and big winners — trend following, breakouts. They demand patience through strings of small losses. Others have a high win rate and small winners — mean reversion, fast intraday trading. They demand iron discipline, because one oversized loss erases ten wins.

The danger in a high-win-rate method is that it feels safe, which tempts you to drop the stop "because it always comes back". That works ten times and wipes the account on the eleventh.

Ten trades tell you nothing. Thirty start to hint. A hundred give a real picture. Until then, don't rewrite the method after every loss — constant tinkering is the surest way to never learn what works.