Fear, greed and FOMO ("fear of missing out") are the three emotional forces that most reliably push a trader to act against their own plan. They are not exotic — they are the ordinary human responses to perceived loss, perceived opportunity, and perceived social exclusion, operating on money and price in real time. Greed makes you want more than the setup justifies; fear makes you protect what you have at the wrong moment; FOMO — a hybrid of the two — makes the absence of a position feel like a loss, so you buy what is already running. The core tension of this whole section is that these emotions are felt most strongly at exactly the moments when the disciplined action is the opposite of what they urge: they peak at tops (greed, FOMO) and bottoms (fear), which is why the same impulses that feel protective or shrewd are, in aggregate, the documented mechanism by which most discretionary traders buy high and sell low. This section is the behavioral layer of Trading Psychology & Discipline — it catalogs how these emotions specifically corrupt entries and exits, and points to the children for the mechanics of each.

The core forces

• Greed — the pull to take, hold, or add to risk beyond what the setup or risk budget supports: oversizing, over-trading, refusing to bank or trim a parabolic move, or holding for a target the structure no longer justifies. Greed lengthens the leash on a position that should be closed.

• Fear — the pull to protect, expressed at the wrong time: selling a valid winner into the first wobble, freezing instead of taking a planned entry, or, paradoxically, the fear of realizing a loss that keeps a losing position open (closing it makes the mistake real). Fear shortens the leash on what is working and lengthens it on what isn't.

• FOMO — the fear that others are profiting from a move you are not in. It converts a missed gain into something that feels like a suffered loss, which behavioral work (regret theory; Kahneman & Tversky's prospect theory) holds is felt acutely. FOMO is what turns a calm observer into a late, reactive buyer. It is amplified by social proof — when peers, media and influencers all appear to be winning, resisting the crowd is hard — and by attention-driven buying: Barber & Odean (2008) document that individual investors are net buyers of attention-grabbing stocks (news, extreme one-day returns, abnormal volume), the exact names a hot move manufactures.

The two altitudes: market sentiment vs. personal behavior

"Fear and greed" appears at two distinct scales, and this section is about the second:

• As aggregate market sentiment — the crowd's collective fear/greed, sometimes packaged into a gauge like CNN's Fear & Greed Index (a 0–100 composite of seven inputs: momentum, price strength, price breadth, put/call options, junk-bond demand, market volatility/VIX, and safe-haven demand; equal-weighted, 0 = extreme fear, 100 = extreme greed). It is used as a contrarian read — Buffett's "be fearful when others are greedy, and greedy when others are fearful" — with extreme readings (commonly cited as <20 or >80) treated as more actionable than the mid-range (CNN labels roughly 45–55 "neutral," below ~45 "fear," above ~55 "greed"). This is sentiment/breadth analysis, and lives in the market-breadth/sentiment branch, not here. The index is a coincident mood thermometer, not a timing signal; it can sit at "extreme greed" for long stretches of a healthy uptrend.

• As personal trading behavior — the same emotions acting on your decisions, one trade at a time. This is the subject of this section. The crowd's greed is a market condition; your greed is a discipline failure. The children dissect the second.

When it matters — and when it doesn't

These biases dominate discretionary, real-time decision-making under open P&L: live entries, live exits, and any moment where an unrealized gain or loss is staring back at the trader. That is where fear/greed/FOMO do their damage. They matter far less — by design — in rule-based or systematic execution, where the entry, stop and exit are pre-committed and the emotional moment has nothing to act on. The entire remedial toolkit across this section reduces to one principle: move the decision out of the emotional moment by pre-defining it in writing (hard stops placed at entry, structural trailing exits, pre-set targets, fixed risk-per-trade), then honoring it. The biases are also weaker for long-horizon, low-turnover investors (Buffett-style guardrails: margin of safety, circle of competence, long holding periods) simply because there are fewer live decisions to corrupt.

Map of this section

The three child nodes are the same emotional architecture — reacting to recent price action instead of executing a plan — expressed at the three points of the trade lifecycle:

• Chasing Entries — the entry-side expression of FOMO: buying late and reactively because price is already moving, rather than at a pre-defined trigger with defined risk. The mechanical cost is a worse fill that silently collapses reward-to-risk. (Distinct from a planned momentum/breakout entry — strength is not the problem; reacting to it is.)

• Cutting Winners Early — the profit-side half of the disposition effect: snatching a small sure gain out of fear of giving it back. Costly because profitable distributions are positively skewed — a few large winners pay for many small losses — so capping winners amputates the right tail where the edge lives (Odean 1998; Shefrin & Statman 1985).

• Holding Losers Too Long — the loss-side half of the disposition effect: riding a loser hoping for breakeven, driven by loss aversion (λ ≈ 2.25 in Tversky–Kahneman 1992) and the reluctance to realize a mistake. The most lethal of the three because a loser held without a stop has no floor.

Together, cutting-winners and holding-losers describe a P&L distribution with truncated upside and a fat left tail — the exact inverse of the favorable skew that trend/swing strategies depend on; chasing degrades the entries that feed it.

Sources

• Shefrin, H. & Statman, M. (1985). The Disposition to Sell Winners Too Early and Ride Losers Too Long. Journal of Finance 40(3). — disposition effect; mental accounting, regret aversion.
• Odean, T. (1998). Are Investors Reluctant to Realize Their Losses? Journal of Finance 53(5). — gains realized at a higher rate than losses (PGR 14.8% vs PLR 9.8% ex-December, i.e. winners ~1.5× more likely to be sold); the winners sold subsequently outperformed the losers held by ~3.4 pp over the following year.
• Barber, B. & Odean, T. (2008). All That Glitters. Review of Financial Studies 21(2). — individuals are net buyers of attention-grabbing stocks; no symmetric attention effect on selling.
• Tversky, A. & Kahneman, D. (1992). Advances in Prospect Theory. J. Risk & Uncertainty 5. — loss-aversion coefficient λ ≈ 2.25.
• CNN Business — What is CNN's Fear and Greed Index, and how does it work? (seven equal-weighted components; 0–100 scale; contrarian use). https://www.cnn.com/markets/fear-and-greed
• Buffett (attrib.), "be fearful when others are greedy…" — contrarian-sentiment framing; widely cited investor maxim.
• Note: the Fear & Greed Index's contrarian efficacy and the "FOMO trades have negative expectancy" claim common in trading-education content are practitioner/folklore-level, not peer-reviewed measured constants — treated as directional, not established, in the child nodes.