Logan - Miller is not totally correct. He is voicing a cliche, that all true in many circumstances, is not universally so. The breakdown of fine motor skills occurs with people are either untrained or emotionally aroused. Training does two things:
1) Trained individuals do not get emotionally aroused in many situations that untrained people do.
2) Trained individuals develop "pseudo-instincts" in which emotional arousal cues an increase in fine motor skills and effective combative abilities. For example, a well-known combatives instructor, after a long period of training a SWAT team hooked them up to heart monitors and led them in a very high stress (potentially painful) training exercise. At the door, right before entry, the average heart rate was 180 beats a minute. They hit the door and achieved 100% kill rate, without no casualties. In highly trained people, stress can activate skills.
Finally, I had the honor, last year of teaching a small aikido seminar at the Akkan dojo in central California. Several of the participants were correctional officers at Corcoran State Penitentiary. And each told me wonderful stories about using classical aikido techniques in very dangerous situations.
As has been said before, the question of how powerful one can become with aikido is governed by how committed one is to your training.
Never heard of an increase in motor skills during a violent encounter other than maybe when receiving an optimal level of adrenaline... Not to say it isn't possible, just never thought of it I guess.
I'd imagine that would come only with a very high level of training.