Sell Rules: Writing Exit Conditions Before You Buy
Worked example: Two investors in the same crash — one had written rules, one did not
By James Ward
TL;DR: The discipline that operationalizes everything else in this cluster is to write your sell conditions at the moment you buy, before you own a single share and before any emotion is attached. You record three specific, observable conditions: what would constitute a broken thesis, at what price or valuation the holding becomes too expensive to keep, and at what size the position must be trimmed for risk. You write them when you are calm, objective, and have no endowment to defend — which is the only time you can think clearly about selling. Then, when news breaks or the price moves, you do not improvise; you consult the conditions, and you act only if one is genuinely met. This is pre-commitment: binding your future, emotional self to a decision made by your present, rational self. It is the same logic as a pilot's checklist or a captain's logbook — a procedure that holds when judgment is compromised by stress. Written sell rules do not remove judgment; they front-load it to the one moment you can exercise it cleanly, and they convert the sell decision from a panicked reaction into the execution of a plan.
Every previous article in this cluster describes a condition under which you should sell. This one is about when and how to define those conditions, and the answer is: in advance, in writing, every time. Without that, the conditions are good intentions that evaporate the moment fear or greed arrives.
The concept in 60 seconds
There is exactly one moment when you can think about selling a position with a clear head: before you own it. At that point you have no loss to avoid, no gain to protect, no endowment inflating its value, and no ego invested in being right. The instant you buy, all of those biases switch on and never fully switch off. So the time to decide what would make you sell is the same moment you decide to buy.
A sell-conditions record has three lines, mapping to the three reasons to sell:
- Thesis broken if: the specific, observable event that would prove the core reason wrong.
- Valuation ceiling at: the price or implied-expectation level at which the forward return no longer justifies holding.
- Trim trigger at: the position size that would breach your risk limits.
When something happens later, you do not ask "how do I feel?" You ask "is a written condition met?" If yes, act. If no, hold. The decision was already made by the version of you best equipped to make it.
Mental model
In Homer's tale, Ulysses wanted to hear the Sirens' song without steering his ship onto the rocks. He could not trust his future self, who would be under the song's spell, so he had his crew bind him to the mast and ordered them to ignore his later pleas. He made the decision while sane and bound his future, compromised self to it. Sell rules are the mast. You write them while rational and let them overrule the version of you that the storm will produce.
The everyday version is a checklist. Pilots and surgeons do not rely on memory and composure during a crisis; they follow a written procedure precisely because high-stakes moments degrade judgment. Your sell conditions are a pre-flight checklist for the position: defined when calm, consulted when not. The point is not that the checklist is smarter than you. It is that the calm you who wrote it is smarter than the panicked you who reads it.
Worked example: two investors in the same crash, one had written rules
Two investors own the same durable business going into a sharp market crash. The stock falls forty percent in weeks.
The first wrote sell conditions when buying: "Thesis broken if the company loses its category leadership or returns on capital fall below the cost of capital for two years; valuation ceiling if the price implies growth above its long-run rate; trim if it exceeds twelve percent of the portfolio." During the crash they pull out the card and check it. Category leadership: intact. Returns on capital: unchanged. Valuation: now far below the ceiling — in fact the price implies almost no growth. Position size: shrunk, not grown. No condition is met. The card says hold, and possibly add. They act on the card, not the fear, and emerge with the position intact.
The second never wrote anything down. Facing the same forty-percent drop with no anchor, they experience only the falling price and the rising fear. With nothing to consult, the decision defaults to emotion, and they sell near the bottom "to stop the bleeding" — converting a temporary, recoverable decline into a permanent, realized loss. Same business, same crash, same starting thesis. The only difference was that one had pre-committed the decision and the other left it to the moment. That difference is the entire value of sell rules.
Historical pattern
Disciplined investors across styles share the habit of deciding the exit before the entry. They write down what would change their mind, what would make a holding too expensive, and how large it is allowed to get — and they revisit those conditions at every review rather than reinventing them under pressure. Their low, deliberate turnover is the visible output of a process that decided the sell question in advance.
The undisciplined pattern is the reverse and far more common: buy on a clear thesis, never define the exit, then make every sell decision in the heat of the moment governed by whatever the price is doing. This is how sound theses become panic sales and how broken theses become permanent holds. The missing ingredient is almost never analysis or intelligence; it is the simple, unglamorous step of writing the conditions down before the emotion arrives.
Decision framework
- Write the three conditions at purchase. Before you buy, record the specific broken-thesis condition, the valuation ceiling, and the trim trigger. No buy is complete without them.
- Make each condition observable. Not "if things go badly" but a concrete, checkable event or level. A vague rule cannot overrule a vivid emotion.
- Tie them to your frameworks. Anchor the thesis condition to the investment thesis, the ceiling to valuation, and the trim to position sizing.
- Consult, don't improvise. When news or price moves, check the conditions before reacting. Act only if one is genuinely met; otherwise hold.
- Revise only with reason, never with rationalization. Conditions can change as the business changes, but update them deliberately at a review — not in the moment to justify a decision you have already made emotionally.
Common mistakes
- No written conditions. The most common failure of all. Unwritten rules vanish under stress, leaving emotion in charge.
- Vague conditions. "Sell if it gets bad" cannot be checked, so it never triggers. Specificity is what gives a rule force.
- Rewriting the rules to avoid acting. Moving the goalposts when a condition is hit is rationalization defeating the entire purpose. Update conditions only at calm reviews, for genuine reasons.
- Setting the ceiling as a round-number price target. Anchor it to value and implied expectations, not "I'll sell at $100." See Taking Profits.
- Writing them and never reading them. The rules only work if you actually consult the card when the storm hits.
How VI Stack uses this
Block 4 makes written sell conditions a required step in opening a position. Before a holding is considered live, the member records a three-sentence thesis and three explicit sell conditions — thesis-broken, valuation ceiling, and trim trigger — and these become the standing reference for every future review. Each review restates the thesis and measures new information against those pre-committed conditions rather than against the price or the member's mood, and an exit must name the specific condition triggered. The system deliberately front-loads the sell decision to the calm moment of purchase, so that later reviews execute a plan instead of improvising under pressure.
What's next
Sell rules are the capstone that turns the rest of the cluster into a repeatable process. Return to When to Sell a Stock for the three conditions these rules encode, and revisit The Endowment Effect for why the rules must be written before, not during. To define the thesis the first rule depends on, see How to Write an Investment Thesis.
FAQ
What are sell rules?
Sell rules are the specific conditions, written down in advance, under which you will sell a position: what would constitute a broken thesis, at what valuation the holding becomes too expensive to keep, and at what size it must be trimmed for risk. They convert the sell decision from an in-the-moment emotional reaction into the execution of a plan made when you were calm and objective. The point is not to remove judgment but to apply it at the one moment — before you own the stock — when it is least distorted by bias.
Why should I decide when to sell before I buy?
Because before you own a position you have no loss to avoid, no gain to protect, and no endowment effect inflating its value — it is the only time you can think about selling clearly. The instant you buy, loss aversion, sunk cost, and anchoring switch on and degrade your judgment, especially under the stress of a falling price. Deciding the exit conditions at the moment of purchase pre-commits the decision to your rational self, so your later, emotional self executes a plan rather than improvising.
What should sell rules include?
Three conditions, each specific and observable: a broken-thesis condition naming the concrete event that would prove your core reason wrong; a valuation ceiling expressed in value or implied-expectation terms rather than a round-number price; and a trim trigger set at the position size that would breach your risk limits. Tie each to its underlying framework — the investment thesis, the valuation, and your position-sizing rules — so the rules are grounded rather than arbitrary.
How specific should sell conditions be?
Specific enough to be checked objectively. "Sell if things go badly" is useless because it can never clearly be said to have triggered, so emotion fills the gap. "Sell if the company loses its category leadership" or "if returns on capital stay below the cost of capital for two years" can actually be tested against reality. A vague rule cannot overrule a vivid feeling; only a concrete, observable condition has the force to do that in a stressful moment.
Can I change my sell rules after buying?
Yes, but only deliberately, at a calm review, and for a genuine reason tied to a change in the business — never in the heat of the moment to justify a decision you have already made emotionally. Conditions should evolve as a company evolves. The danger is rationalization: moving the goalposts the instant a condition is hit so you can avoid acting, which defeats the entire purpose of writing them down. Update with reason, not with convenience.
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