The context of the following conversation is Alex was about to make meatballs but he didn't want his sleeves to get dirty so he rolled them up.:
Alex says The sauce from these meatballs always ruins my shirt.
The friend responds Don't be a wimp dude it's just pasta sauce.
Alex responds Yeah well this is my lucky shirt. I only have one of these.
The friend responds Buy a new one if that one gets ruined.
Alex responds You don't understand. I have scored 100 on every chemistry test by wearing this shirt. I cannot afford to have it ruined.
The friend responds Well okay. You wouldn't want to ruin that shirt then. That's some great luck.