The more relaxed the muscles are, the more energy can flow through the body. Using muscular tensions to try to 'do' the punch or attempting to use brute force to knock someone over will only work to opposite effect.
Bruce LeeForget about winning and losing; forget about pride and pain. Let your opponent graze your skin and you smash into his flesh; let him smash into your flesh and you fracture his bones; let him fracture your bones and you take his life! Do not be concerned with escaping safely- lay your life before him!!
Bruce LeeFor it is easy to criticize and break down the spirit of others, but to know yourself takes a lifetime.
Bruce Lee