Sometimes a student, who is normally an excellent sparring competitor, consistently loses against certain inferior opponents. The student may be physically better than these opponents, technically better than these opponents, and better prepared than these opponents, but the student still loses. Something about certain opponents freaks out the student so he or she loses concentration.
It is obvious that something other than physical ability is causing these students to mess up while performing patterns, to fail to accomplish their breaks, or to lose their sparring matches against lesser opponents. That something is mental preparation and concentration.