YOU SAID:
I ate my pizza when I wasn't supposed to.
INTO JAPANESE
私はピザを食べたのはずではなかった時でした。
BACK INTO ENGLISH
It was when I shouldn't have eaten pizza.
INTO JAPANESE
ピザを食べるべきではなかったときでした。
BACK INTO ENGLISH
It was when I shouldn't have eaten pizza.
You've done this before, haven't you.