When, quite literally, a person is pissed off so bad that they cannot mentally, emotionally, or physically (teehee @ pun) take it anymore.
K': You're such a fuck up. I think you fail at life. You're the biggest loser I've ever met. Your IQ is the equivalent to an apple.
Random Girl: ZOMG I CAN'T TAKE IT ANYMORE! STOP INSULTING ME BEFORE I SNIP YOUR BABY CARROT OFF!