What is Sunk Cost Fallacy?
Sunk cost fallacy continues because you already invested time, money, or ego — past cost should not drive exit.
Formula
Wrong Question (Sunk Cost Thinking): "I've invested $1,000 and am down $300. How do I recover that $300?" Right Question (Forward-Looking): "I have $700 in this position. Is this the best use of $700 right now?" The $300 loss is gone regardless of what you do. Your entry price doesn't affect the stock's future.
Indian market context (NSE)
Reference levels: Nifty 50 at 24,300, Reliance Industries at ₹1,300, Bank Nifty futures at 55,000 (lot size 30). Examples below show how Sunk Cost Fallacy shows up on Indian index, equity, and futures books — update to live quotes in your journal.
Nifty 50 perspective
Sunk Cost Fallacy often appears after Nifty moves 150+ points from open while you waited — journal “Nifty FOMO” entries separately from A-grade setups at 24,300 levels.
Reliance Industries perspective
Sunk Cost Fallacy on Reliance trades is common around results noise at ₹1,300 — rate discipline 1–5 in TradeLyser even when P&L is green.
Bank Nifty futures perspective
Sunk Cost Fallacy after Bank Nifty whipsaws 200 points around 55,000 triggers revenge sizing — enforce max daily loss before re-entering MIS.
How to validate
- Validate Sunk Cost Fallacy tags against time-stamps — impulse entries cluster after losses.
- Compare P&L on tagged vs untagged sessions over 20+ trading days.
- Use mentor review to confirm tag definitions stayed consistent.
- Do not validate solely on one exceptional week of discipline.
How to track in TradeLyser
- Add psychology grade and Sunk Cost Fallacy-related tag on each trade card.
- Use daily journal mood line when Sunk Cost Fallacy risk is elevated.
- Dashboard: count psychology violations per week alongside P&L.
- Share tag definitions with mentor before monthly review.
Best practices
- Separate process score from P&L when reviewing Sunk Cost Fallacy.
- Use cooldown timers after rule breaches involving Sunk Cost Fallacy.
- Sleep on size increases — never add risk the same day as a Sunk Cost Fallacy violation.
- Celebrate disciplined losses that followed the plan.
Common pitfalls
- Labelling trades after the fact to match desired self-image.
- Increasing size to fix a Sunk Cost Fallacy episode immediately.
- Confusing a green day with cured Sunk Cost Fallacy behaviour.
- Skipping tags on “small” impulsive trades.
How to use this in TradeLyser
Tag “held for breakeven” exits; review damage to R versus cutting at plan stop.
Related terms
Anchoring bias overweights the first number encountered — purchase price, IPO, or morning high — in later decisions.
Loss aversion is the tendency to feel losses more strongly than gains, leading to holding losers or avoiding valid risk.
Mental accounting is treating rupees differently by source or account — “house money” from morning wins.
A stop loss is a pre-defined exit when the market moves against you by a set amount. It caps loss per trade when fills match your plan.
FAQ
Averaging down sunk cost?
Adding to losers doubles fallacy — tag adds separately.
Long-term investing excuse?
If trade tag is swing, do not switch story to “investor.”
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