5.9. Selling from Fear or Buying from Euphoria
Lesson objective
Control emotional decisions.
Losses create pain, and rising prices create excessive confidence. Both emotions can pull investors away from their process.
A written thesis, reasonable position size, and predefined monitoring criteria help a person respond to facts instead of impulses.
If a decline harms financial capacity or prevents sleep, the risk taken may exceed tolerance or capacity.
Emotion becomes expensive when it changes the process
Fear and euphoria are normal. The mistake is allowing them to replace a predefined decision process.
| Event | Emotional impulse | More useful response | |---|---|---| | Stock falls sharply | “Get out now” | Check whether thesis evidence changed | | Stock rises sharply | “Buy before I miss it” | Recalculate valuation and expected return | | Bad headline | “Everything is broken” | Quantify financial impact and persistence | | Great earnings | “Nothing can go wrong” | Compare results with expectations and risks |
Separate price change from thesis change
Price change ≠ Business change
But sometimes:
New fundamental evidence → Business-value change → Price may react
A drawdown can improve or worsen the opportunity
If a stock falls 25% while the business thesis and long-term cash-flow outlook remain intact, expected return may improve because the price is lower. If it falls because the company's competitive advantage has materially deteriorated, the lower price may simply reflect a lower value. The chart alone cannot tell you which case you are in.
Pre-write the conditions that would make you add, hold, reduce, or reassess. Rules written when calm are easier to follow when the market becomes emotional.
What you should remember
- Design the process before volatility arrives.
Practice
Write rules for reviewing a holding after a large rise and after a large decline.