Hesitation is expensive and invisible. The trades not taken do not appear in the record, so a trader can conclude their strategy has stopped working when in fact they have stopped taking it.
It follows losses, follows a large drawdown, and follows any trade that hurt more than expected. It is also strongly connected to size: a position large enough to matter is a position you will hesitate on. See scared-money.
Two remedies. Reduce size until pulling the trigger is easy, then rebuild. And log every qualifying setup whether or not you took it, so hesitation shows up as a number rather than as a feeling.
Related: scared-money, undertrading, freeze-response, patience