I'm going to ostracize one of my friends
Did your friend so something bad to you?
He ate a steak without saying anything and I thought the steak was mine.
You shouldn't ostracize someone over something that trivial. Talk to your friend and politely explain that the steak was yours. I'm sure he'll understand.
I don't give-fucks anymore
You shouldn't drop a friendship over a steak. Let him know it was yours and tell him politely not to eat your food. And think about how minor a thing this is in the grand scheme; do you really want to end a friendship over it?