The Sunk Cost Fallacy in Trading: Why You Hold Losing Positions Too Long.
By Sofia Harchich | Trading Psychologist & Behavioral Finance Writer | thewealthmirror.com
The position isn’t being held because the analysis still supports it. It’s being held because closing it would mean admitting the money is already gone.
There’s a specific kind of stillness that happens when sunk cost fallacy in trading behaviour takes hold — when a losing trade has been open too long. The original thesis stopped applying days ago. The stop-loss has been moved twice. And yet the position stays open — not because new evidence justifies it, but because closing it would make the loss real.
This is the sunk cost fallacy in trading, and it’s one of the most expensive patterns precisely because it disguises itself as patience. “I’ll give it a bit more room” sounds like discipline. Often, it’s something else entirely.
What the Sunk Cost Fallacy in Trading Actually Looks Like.
The sunk cost fallacy is the tendency to keep investing time, money, or effort into something based on what’s already been spent, rather than on the current and future value of continuing.
In trading and investing, it shows up as:
- Holding a losing position because “I’ve already lost so much, I can’t sell now”
- Adding to a losing trade to lower the average cost, without new evidence supporting the original thesis
- Refusing to cut a position because of the hours spent researching it
- Staying in a trade past the original exit plan because exiting would “waste” the conviction that led to entering
The fallacy isn’t really about the money already lost — that money is gone regardless of what happens next. It’s about what closing the position would mean about the decision to open it.
The loss already happened. The only thing still being decided is whether to lose more.
Why This Bias Is So Hard to Override?
Behavioral economists Daniel Kahneman and Amos Tversky identified loss aversion as a core finding of prospect theory: people feel the pain of a loss roughly twice as intensely as the pleasure of an equivalent gain. The sunk cost fallacy is loss aversion’s accomplice — it gives the brain a reason to delay the moment the loss becomes final.
There’s also an identity component. Closing a losing position can feel like confirming “I was wrong,” and for traders who’ve built confidence around being right, that confirmation feels disproportionately threatening. The position stops being about the market and starts being about self-image.
A third layer: the more effort that went into the original decision — the research, the conviction, the conversations defending the trade — the harder it becomes to let go of it, simply because more has been invested in being right.
Closing the trade was never the hard part. Admitting the thesis changed was.
How to Catch It Before It Costs More?
- Ask one question before adding to or holding any losing position: “If I had no position right now, would I open this trade today?” If the answer is no, the only thing keeping it open is the sunk cost.
- Separate the decision to exit from the feeling of being wrong. Exiting a trade is a risk management decision. It is not a verdict on your competence as a trader.
- Pre-define your invalidation level before entering, and treat it as non-negotiable. The sunk cost fallacy thrives in the gap between “my plan said exit” and “but I think it’ll come back.”
- Track time-in-trade against original thesis, not just price. If the reason for the trade no longer holds, the position has already been invalidated — regardless of where price sits.
- Notice the specific language you use about a losing position. “I’ll give it a bit more room” and “the market just hasn’t caught up yet” are common tells that the decision is being driven by what’s already been spent, not what’s likely to happen next.
The Deeper Layer: What the Trade Is Really Defending.
Underneath the sunk cost fallacy in trading is usually a more personal resistance — to admitting that a belief, once held with conviction, no longer matches reality.
This is where Jung’s concept of the shadow becomes useful: most people aren’t aware of how much their decisions are organized around protecting a self-image, rather than around the facts in front of them. A trader who has built an identity around being analytically rigorous may find it harder to exit a losing position than a trader with less invested in being “the smart one” — because the exit isn’t just a trade decision, it’s a small confrontation with a part of their self-concept.
Eckhart Tolle’s writing on presence offers a useful reframe here: the position only feels unbearable to close because attention is fixed on the past decision rather than the present evidence. The market doesn’t know or care what was spent to get here. Neither does the next trade. The only question that matters is what the current evidence actually supports — and that question is always available the moment attention returns to it.
Start Here:
- Find one position in your portfolio right now that you’d be reluctant to re-enter today
- Ask whether you’re holding it for the thesis or for the sunk cost
- Write your invalidation level down before your next entry — and commit to it before, not after
- Notice the language you use about losing positions this week; “more room” and “hasn’t caught up” are signals worth catching
The position was never really about the chart. It was about whether the money already spent gets to decide what happens next — and it doesn’t, unless that’s allowed. The trade that’s hardest to close is usually the one with the most to teach about what’s actually being protected.
This is what sunk cost fallacy trading costs traders most: not the loss itself, but the refusal to let it be over.
✨Discover which pattern is running your trading: thewealthmirror.com/quiz.
About the Author
Sofia Harchich is a Trading Psychologist and Behavioral Finance Writer with a Master’s in Psychology. She works at the intersection of Jungian shadow work, neuroscience, and market behaviour — helping traders understand the psychology driving their decisions, not just the strategy.
Read more at thewealthmirror.com/about
