Karate is a martial art that relies on precision and one's own power to achieve unusual feats of strength, i.e: karate chopping a piece of wood. The message can be asking you to focus only on your power to achieve, and not on the obstacles, or the idea of failing. Failure is an illusion when you are focused on learning and succeeding. One does not learn karate overnight however, much practice and patience is needed.
Another aspect of karate is how one learns to use the momentum of another's attack to leverage and turn the force back on the opponent. If nothing anyone says or does can make or break your day - that is real power. Dreaming of karate can be a message about the Eastern philosophy of 'not doing' or not being so reactive.