You can have a 60% win rate with great entries and still blow up your account. How? Bad position sizing. Position sizing is the most underrated skill in trading. Most traders obsess over entries — the perfect setup, the ideal indicator — while casually deciding "I'll take 5 contracts" based on how confident they feel. That confidence-based sizing is one of the most expensive mistakes in trading. ## Why Position Sizing Matters More Than Entry Consider two traders with identical trade selection: **Trader A (Consistent Sizing):** - Always risks 1% of account per trade - 100 trades, 55% win rate - Average win: $200, Average loss: $180 - Result: +$1,100 **Trader B (Emotional Sizing):** - Risks 0.5% when unsure, 3% when "confident" - Same 100 trades, same 55% win rate - But "confident" trades cluster after wins (overconfidence) - And confident trades that lose are 3x the damage - Result: -$400 Same trades. Same win rate. Completely different outcomes. The only variable is sizing. ## The 5 Most Common Position Sizing Mistakes ### Mistake 1: Sizing Based on Confidence "I'm really sure about this one, so I'll size up." This is gambling psychology, not risk management. Your confidence level has zero correlation with trade outcome. In fact, overconfidence after wins typically leads to the largest individual losses. **What it looks like in data:** - Position sizes vary 3-5x between trades - Largest positions cluster after winning streaks - Largest losses come from the largest positions ### Mistake 2: Increasing Size After Losses "I need to make back what I lost, so I'll double my next trade." This is the martingale fallacy. Each trade is independent. Doubling down after a loss doesn't increase your probability of winning — it increases your probability of a catastrophic loss. **What it looks like in data:** - Position sizes increase immediately after losses - The worst drawdowns come from the post-loss size increases - Recovery periods are longer because single