- Committing a large sum to a first trade before understanding how the market and execution costs work.
- Doubling down on a losing position in the hope of recovering — adding risk to risk, not correcting the decision.
- Using high leverage before results have settled over months.
- Neglecting a stop loss on short-term positions.
- Adjusting the portfolio too often — every trade has a cost, and periodic review serves better than minute-by-minute watching.
The thread running through all of them is the same: a decision taken under the pressure of the moment is worse than one written down in advance.