The fact that the bag can't strike you back -" perfecting faults"
Always keep well covered and never leave yourself open for one moment.
The power of the punch and kick comes not, as so many people imagine, from vigor with which the blow is struck, but by correct contact at the right spot at the right moment, and with feet and body in correctly position and balanced.
Move! Move! Move around the whole time, side stepping, feinting varying your kicks and blows to the movement.
Remember that the body is an integral part of the kick and punch, it is not only the leg and arm that delivers them.