Eight Investing Mistakes That Cost Real Money
Most damage comes from behaviour, not from picking the wrong fund.
At a glance
Figures checked 1 Sep 2026
Risk level
Behavioural risk is the largest and least measured
What to take away
- Selling in a downturn converts a paper loss into a permanent one.
- Chasing last year's best performer buys the performance that already happened.
- Waiting for certainty means buying after the recovery, not before it.
- Selling during a decline. The market recovers on a handful of unpredictable days, and they cluster near the worst ones.
- Chasing performance. Rankings reshuffle; buying last year’s winner is buying high.
- Holding a large cash position while waiting for clarity. Clarity arrives priced in.
- Ignoring fees because the percentages look small.
- Over-concentrating in your employer’s stock, which ties your job and your savings to the same outcome.
- Trading around news. Prices reflect the news before you finish reading it.
- Neglecting the account type and paying avoidable tax.
- Having no written plan, so every decision is made from scratch during a stressful week.
One page describing your allocation, contribution rate and rebalancing rule removes most of these. Write it while markets are calm.
Common questions
A downturn is when your regular contributions buy the most shares. Stopping converts a long-term advantage into a loss.