Eat ass or become ass
You yell it when you're about to do something so idiotic it might get you killed or make you the most embarrassing person in the game.
"Eat ass or become ass" before I tried to fight five enemies with no weapons.
"Eat ass or become ass" as I ran into a room with no plan.
"Eat ass or become ass" as I tried to sneak up on a sniper and got shot in the face."