Bruce Lee recognized as well the fact that there is no defednse against an unexpected attack, which is why he stressed not finding oneself in condition white if at all possible.
For more on this, you might want to check out "The Tao of Jeet Kune Do" and "Bruce Lee's Fighting Method." Of course no one can be prepared 100% of the time, but you can minimize your exposure. The Seven Samurai was a great movie, by the way. Toshiro Mifune as the lout who fails the "test" in spectacular fashion was priceless.