There are reasons the same mistakes repeat. Knowing where things bend helps you bend less.
At the same amount, losing hurts more than gaining pleases. That makes realising a loss unusually hard. Not selling feels like not having lost yet, but the account is worth the same whether you sell or not. It is easy to miss that choosing not to sell is itself an active decision to keep holding.
Selling profitable positions quickly to lock in gains while holding losing ones waiting for recovery is a repeatedly observed tendency. Doing so removes what is working and leaves what is not. The problem is that the basis for the decision is your purchase price rather than the outlook for the holding.
After buying, information confirming the decision registers more easily. Contrary information looks weakly supported, and you gravitate toward opinions on your side. This is not a matter of willpower but a basic tendency in how people process information. Deliberately seeking and writing down the counter-case is the response that works.
Many people doing the same thing is not evidence that the judgement is correct, yet it is reassuring. Watching something rise quickly creates a sense of missing out, and that sense peaks when the price has risen most. That is the structure by which the latest entrants are hurt worst.
Trying not to feel does not work. Setting criteria before the feeling arrives does. Writing down why you bought, what would show the judgement was wrong, and the maximum allocation means comparing against what you wrote rather than how you feel. This explains common biases; it does not address any particular holding or moment.
The more often you check your account, the more often you experience a loss. The same asset shows many down days when viewed daily, while over several years the swings feel much smaller. Combined with the tendency to feel losses more than gains, frequent checking makes you more anxious regardless of actual results, and impulsive trades increase. If you invest on a long-term plan, deliberately lengthening how often you check helps manage emotions. Simple steps like turning off price alerts or moving the app off your home screen work better than you might expect.
People tend to use the first number they encounter as a reference point and judge around it. A past all-time high, a target price someone published, and the price you first paid all become anchors. A stock far below its peak feels cheap, but if that peak was an overheated price, the lower price may still be expensive. Conversely, an asset that has risen a lot can look too expensive because of the price you first saw, and you miss the chance to reassess it. Simply being aware of the anchor helps, as does the habit of asking what a price is based on rather than how it compares.
The tool that most consistently reduces bias is a written record. Each time you buy or sell, jot down the date, amount, reason, how you were feeling, and the conditions under which you would consider the decision wrong. Reading it a few months later shows that some decisions with good outcomes had flimsy reasons, and some with bad outcomes followed a sound process. Practising separating outcome from process reduces hindsight bias. The journal isn't for anyone else, so it needn't be long — three lines are enough.
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