i think, but am no expert.
i think that Calm Mind is a Requirement for Training.
(especially with Weapons, which are harder to Wield & Control than just one's Physical Body).
Otherwise, imprecise, faulty moves are being 'Programmed' into Nervous System & Muscular Behaviorism.
Training should start from slow, simple, but Very Precise & Focused Moves, trained MANY times, then the Speed of Training & Effort can increase.
Goal of this method is to not lose Focus & Precision, and have these Focused & Precise Moves as a part of one's Fighting Style.
With many attempts, body adapts. Muscles are stronger, more enduring, better adopted to fast moves of certain types, nervous system carrying the information better... better coordinating many muscles & faster to fight together, without opposing each other. if neccessary, properly trained nervomuscular system can change moves faster - for example to detract route of a strike by an angle. i think this has use in misdirection (You pretend to Perform a Strike without knowing for sure where it will land, then as You observe opponent, adjust it 'on the fly' if neccessary).
Also, anger during fight makes combat skills more Unreliable.