The most expensive decisions in any market are not the wrong ones — they are the ones made in the wrong two weeks.
The fall
Price drops sharply. Headlines say what everyone already knows. The feeling is that something has gone wrong with the thing itself, rather than with the price of it. Selling converts a paper loss into a real one, at exactly the moment you have the least information and the strongest feeling. The arithmetic of what a 50% fall requires to recover is in compounding, and why it misleads.
The rise
The mirror image. Price rallies, everyone is confident, and the risk is increasing the size of a position at the point where the least bad outcome is average.
What actually causes both
A decision made in the moment, by a person whose plan was never written down. The feeling is not a signal about the market; it is a signal that there was no plan to follow.
The one intervention that works
- Write your plan when nothing is happening — amount, plan, horizon, and what you do in a fall. The full version.
- Decide in advance what would make you change it, and write that too. It will be something about your life, never the price.
- Remove the feed during the bad weeks. This is the hardest and the most effective.
- Review monthly on a fixed day, not on the days the market moves.
None of this makes the market behave. It only stops you from making a decision in the one fortnight when making one is most expensive.