Position sizing usually matters more than entry timing for long-run performance. Mechanism: A well-timed entry at too large a size can destroy a portfolio. A mediocre entry at appropriate size survives and lets the thesis work. That is why professional risk management starts with "how much" before "what" or "when." Market translation: Sizing a single stock position at 25% of the portfolio turns any -20% stock decline into a -5% portfolio hit. At 5%, the same decline costs only -1%. $$ Max\ Position = \frac{Portfolio\ Risk\ Budget}{Expected\ Position\ Volatility} $$ Plain English: Size should be set by how much risk the portfolio can absorb, not by how confident you feel. Failure mode: The mistake is perfecting the entry signal while ignoring whether the position size allows recovery from being wrong. Review question: Ask whether the market is mispricing the mechanism or simply narrating it loudly. That is usually where the edge is: not in the vocabulary, but in the structure underneath it.