A precise definition of edge
An edge is a positive expected return per decision: on average, across many repetitions, each position you take is worth more than it costs. That is it. It is not a hot streak, a good week, or a strong feeling about a game. It is a structural advantage — usually a more accurate probability estimate or a better price — that pays off over a large sample even though any single result is random.
Why a winning week proves nothing
Variance is loud and edge is quiet. A coin-flip strategy with no edge at all will still produce winning weeks, winning months, even the occasional winning year. So a stretch of profit is genuinely weak evidence of skill on its own. This is the trap that ruins beginners: they mistake a lucky sample for a real edge, scale up, and hand it all back when variance turns.
The honest tests for a real edge
Three checks matter. First, sample size: dozens of decisions tell you almost nothing, hundreds start to. Second, a forward-looking metric like closing line value, which grades your decision quality independently of whether the result landed — consistently beating the closing price is strong evidence of edge even before the profits show. Third, a written, repeatable process, because an edge you cannot describe is one you cannot trust or reproduce.
Stay humble about it
Real edges are smaller and rarer than most people assume, and they can fade as markets adapt. Treat your edge as a hypothesis you keep testing rather than a fact you have proven once. The investors who last are the ones who demand real evidence before they believe in their own skill — and keep demanding it as they go.