The order was sitting there, partially filled, bleeding. I'd entered a mid-cap resources stock on what looked like a textbook breakout — clean chart, strong volume spike on the signal candle, solid sector momentum. What I hadn't done was check the average daily volume against my intended position size. Rookie arithmetic. Fifteen years in and I still skipped the step.

My position represented roughly 18% of that stock's average daily turnover. I wasn't trading the market. I was the market. Every attempt to exit moved price against me, which made the exit worse, which made me hesitate, which made it worse again. The spread alone was eating 0.4% per attempt. That's not a trade. That's a hostage situation.

CONCEPTLiquidity determines whether your strategy works in theory or actually works.
WARNINGIf your position size exceeds 5% of average daily volume, you don't have an exit — you have a wish.
KEY IDEAA great entry means nothing if the market can't absorb your exit without you paying for the privilege.

The root cause wasn't greed. It wasn't overconfidence. It was a single skipped calculation — position size as a percentage of average daily volume. I had a rule for entry filters. I had a rule for stop placement. I had no rule that said: if this position is more than 5% of ADV, it doesn't qualify. That gap in the checklist cost more than the loss itself, because it meant the same mistake was structurally possible every single session.

Position Size vs Exit Cost (illustrative)0%1%2%3%1%5%10%15%20%Position as % of Avg Daily VolumeDanger zoneSpreadSlippage

The fix was unglamorous: a mandatory ADV filter added to the pre-trade checklist, sitting above entry criteria. If the intended size exceeds 5% of the 20-day average daily volume, the trade is disqualified — full stop. Understanding how market liquidity affects execution cost is foundational, not advanced. The mechanics of bid-ask spread widening under thin conditions are well documented, and the broader concept of market impact explains exactly why large orders in illiquid stocks destroy their own execution quality.

A perfect setup in a market that can't absorb you isn't an opportunity — it's a trap you built yourself.

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