We have all heard about things like tunnel vision, freezing up, losing small muscle control due to adrenaline and our bodies natural response to stress, all factors that work against applying the principles of Aikido to a situation. What do you do to minimize or eradicate this natural biological response?
Does your dojo feature reality simulations, simulated muggings or assaults? If not, what aspect of training do you feel helps you overcome these things the most?
In my experience, adrenaline gives complete opposite effects. The pupils open up, the mind slows down and breathing comes to a more natural state. Not unlike the effect of certain prohibited stimuli...
What you describe is more of a fear reaction. By training a martial art, not necessarily aikido, you eventually get a foundation, or a reservoair, that you can use to support yourself in a stressful situation. Still, the only way to work on this natural instinctive reaction is to experience stressful situations and learn from them.
A personal observation: the breathing part is extremely important. I've been a doorman for a couple of years now and I noticed that if I had been smoking or using chewing tobacco just before a situation, this affected my circulation and oxygene levels in such a way that I was less ready for the situation. In other words, not being able to transport the necessary oxygene around my system hindered the natural body response of alertness and confidence...