You Only Live Once. A stupid motto that countless teenagers live by because it gives them the excuse to be promiscuous, commit crimes, drink underage, do drugs and deny responsibility for their actions.
"LOL I totally just put some guy's window through. YOLO."
"You know when you hit Brad in the head with a cricket bat?"
"He died in hospital last night. The police are looking for you"
"Oh well YOLO."