Once a trader is long, every bullish indicator looks meaningful and every bearish one looks like noise. Confirmation bias is why traders hold through a broken stop-loss level and why chart patterns look so clear in hindsight.
Writing the invalidation condition down before entering is the practical defense: at what price, exactly, are you wrong?
Example: a trader long a stock reads six bullish social posts and dismisses the company's guidance cut as already priced in. The stock falls another 20%.
Related: hindsight-bias, overconfidence, trading-plan, sunk-cost-fallacy