Variance

Variance is the thing that lets a coin-flip bettor go on a heater and feel like a genius, and a genuinely sharp one stare at a red graph for two months.

Even with a real edge, results scatter around your expectation in the short run. Win streaks and cold runs aren't signals that your method started or stopped working; they're the normal noise of a probabilistic game. The edge only shows once the sample is big enough to drown the noise out.

This is why we keep coming back to closing line value and large samples. They're a couple of the few things that tell you something true while variance is busy lying to you about everything else.