A recent quote read at the Chiron blog by Rory Miller turned on a light. "If something is predictable, it is preventable." Think about that one and what it means to have the ability to predict bad things as it relates to self-defense.
Another quote I liked, "Reliability ..... this one is endemic in the martial arts. It is possible to know an awful lot of things that are not true. It is always hard to measure the reliability of your own beliefs."