Mind Under Stress
The mind can go either direction under stress — toward positive or toward negative: on or off. Think of it as a spectrum whose extremes are unconsciousness at the negative end and hyperconsciousness at the positive end. The way the mind will lean under stress is strongly influenced by training.
Not in a duel yet
Source: Dune, by Frank Herbert, 1965; Ace Special 25th Anniversary Edition, p262