Self-talk comes in two forms. Judgement talk evaluates you - idiot, you always do this, you are never going to get this right - and raises arousal while adding nothing. Instructional talk describes the next action - check size, wait for the close, the stop is set - and reliably improves performance on complex tasks.
The shift is from commentary to procedure. It is easier when the procedure exists: a trader with written rules has something concrete to say to themselves, while a discretionary trader with no plan has only opinions about their own character.
Notice the tone after losses in particular, since that is where judgement talk concentrates and where it feeds the shame-spiral.
Related: shame-spiral, mindfulness-practice, affect-labelling, implementation-intention