Even if you get the first shot in, there’s no guarantee that the persons friend won’t hit you in the back of the head with a bottle of beer and leave you struggling with a nasty concussion. Or the person you hit strikes their head on a hard surface, killing them. Or some cop or DA decides to make an example of your assault case, and you lose your job or have to do jail time. Just because you only intended to throw a punch doesn’t mean things can’t go badly out of hand.