I was in a little bar in Lafayette, Louisiana when I was 18 and homeless.
On that particular night, that bar was selling all you can drink Miller light draft for $5 till 11pm or the kegs were dry. Each bar in the area had a special like that one night a week which is why I was THERE, having sold my blood plasma for $20 earlier in the day and had already spent most of that on food, probably a shrimp Po Boy.
This place, you walked in and you were at the bar, turn left to get to tables and the juke box.
Sitting at the bar this angry guy came up to the fella next to me and started airing his grievances about disrespect or some woman he fancied, I dunno, maybe drugs or money? Why do idiots act like idiots? Usually something to do with some of that.
The dude at the bar wasn't shook though, he says "whoa, hey, calm down, bro. Let me buy you a real beer and let's talk about this. Bartender, two cold mugs of Heineken."
So bartender pulls two glass mugs out of the cooler and fills em up, hands em over.
The guy I was sitting with picks his up, holds it up for a cheers, they clink glasses, they tap the bar with the mugs.
Then the angry guy put his mug to his lips and tilted his head back to drink, and the other guy took his own full mug of beer and smashed it into the glass in the other guys face. Shattered it. Stunned him. Knocked him out of the chair onto the ground with a face full of blood, screaming in pain.
He kicked him in the head on the way out the door, never saw either of them again.
I guess the moral is never take your eyes off your enemy, and always smile when you're planning something sinister.