A fixed pre-trade routine (market check, re-reading your rules, setting today's risk limit) is a proven way to reduce emotional variance.
Executive Function and Decision Fatigue
Psychological research on "executive function" shows that decision-making depletes throughout the day (ego depletion). Forcing yourself to figure out "what now?" from scratch during a session leads to mental fatigue and emotional calls. Deciding rules in advance and acting like an "execution-only robot" during the session is the optimal design to lower cognitive load.
Minimal Winning Routine
1) Review yesterday's trades. 2) Confirm today's scenario and invalidation lines. 3) Write down your risk limit. These three steps are enough.