The most effective fighting techniques are useless when not executed with correct timing.
Timing means to regulate actions, or to pace one's movements, to achieve the most desirable result.
It is a principle of coordination which we must come to understand. A fight is the perfect tool to learn correct timing because it creates a scenario in which one must harmonize one's movements with the opponent's, or get hit. One of the most important aspects of this principle, is its relation to our reactions. A fighter must react at the precise moment in order to defend against an attack. To hesitate in combat is to kneel before the executioner.