Three diagnostic questions to ask yourself when a position trades against you: (1) Has the specific operational driver I named at initiation changed? (2) Has the bear case I named at initiation become more likely than I initially assessed? (3) Has a new bear case emerged that I did not initially price in? Answers in order of severity. Q1 yes = thesis broken. Q1 no, Q2 yes = thesis under pressure, re-size. Q1 no, Q2 no, Q3 yes = new overlay, re-evaluate. Q1 no, Q2 no, Q3 no = market disagreement, do not act on price.
| Diagnostic | Broken thesis (Q1 yes) | Disagreeing market (all no) |
|---|---|---|
| What changed | The specific operational signal you named is moving against you (e.g., margin contraction widening, churn accelerating) | Sector de-rating, macro rotation, technical flow — none of which touches the operational signal |
| Who is right | The market saw something you missed in the operational walk | You saw something the market is currently discounting at a different rate |
| Action | Exit decisively at the size you would size a new position with the new evidence — usually that is zero | Re-run the asymmetry math at the new price; add if the trade passes the same hurdle as initiation |
| Failure mode | Refusing to exit because the price is below your cost basis (anchoring bias) | Exiting because the price is below your cost basis (loss aversion masquerading as discipline) |
The anchoring trap. Your original entry price is irrelevant to today's decision — it is sunk cost. The only price that matters is today's price relative to today's fair value given today's evidence. If you would not initiate the position at today's price with today's evidence, exit. If you would initiate it, hold or add. The fact that you happen to own it at a higher cost basis is not an analytical input.
Worked example — Hartwood Systems. Initiated at $54 on the thesis that the new CFO would tighten working capital and drive multiple expansion as inventory turns moved from 4.1x to 6.0x over twelve months. Three months in: stock at $42, inventory turns at 4.9x (on track). Software sector down 18% on rate-cut delay. Diagnostic: Q1 no (operational driver intact), Q2 partial (the sector overhang is a new bear-case overlay the original thesis under-priced), Q3 yes (rate-cut delay is a new macro overlay). Action: re-run asymmetry. New bull $68 (50%), new base $58 (35%), new bear $36 (15%). Reward to bull ($26) vs downside to bear ($6) at $42 is 4.3x; this passes the initiation hurdle. Decision: add to position, but at the same starter-sized increment as a new initiation rather than averaging-down to the original target.
## See also: deeper references - **Variant-perception framework:** `ptk-2` in `practitioner-toolkit-201` — for the differentiated-view discipline that thesis-drift checks rest on. - **DCF sensitivity to operational driver:** `dcf-201` and `pv-1` in `corpval-advanced-301` — for how to re-run the valuation when the catalyst slips or accelerates. - **The anchoring bias trap and disposition effect:** `bf-3` in `behavioral-finance-201` — for the behavioral foundation of why investors over-hold losers and under-hold winners. - **Catalyst windows and the patience trap:** `ptk-3` in `practitioner-toolkit-201` — for the diligence-versus-action discipline. - **Macro overlays and multiple-de-rating mechanics:** `mac-3` and `macro-101` — for how rate moves drive cross-sectional multiple compression that is unrelated to operational performance.
Sit with the ideas.
Hartwood Systems is down 22% since you initiated three months ago. The original thesis was that a new CFO would tighten working capital and re-rate the multiple inside twelve months. The CFO has executed on inventory turns (the operational signal you named as the catalyst). The stock is down because the broader software sector has de-rated by 18% on a rate-cut delay. Which of these is the practitioner-grade read?