Don't stop, get the adrenaline flowing; knock him down, keep you're fists, knees and legs thrashing until he a) runs away b) surrenders or c) stops moving completely. It's the basic concept of self defense. One particular move I am a big fan of is such that you can crush his windpipe in about 10 seconds. He will hopefully survive with an ambulance, but he will never forget it his whole life.
Good grief! Never punch anyone in the windpipe, that's unless you'd like to spend some time at Her Majesties Pleasure [TM]

I wonder why I bother sometimes.