Maximum adverse excursion is the largest drawdown a position showed while you held it. The one metric that justifies a stop decision, and the one misapplication that makes it worthless.

The most expensive stretches often sit just behind the best ones. Three measurable traces reveal the pattern, short arithmetic demystifies the streak, and three rules take position size out of the moment.

Expectancy tells you what one average trade is worth. The formula with an example, how it differs from profit factor and R multiples, and why a good figure can still not be worth the effort.