Confirmation Bias

Confirmation bias is the tendency to seek out, notice, and weigh information that supports a position you've already taken (or want to take), while discounting evidence that contradicts it. In trading, this often shows up as ignoring a stop-loss signal or ongoing warning signs because they conflict with a trade you're emotionally attached to. Systematic, written entry and exit rules are one of the most effective defenses, since they remove room to selectively interpret evidence once a position is already open.