如果有人忽悠你去做某件事，但是你早就看穿了其中的陷阱，你就可以说"I was not born yesterday."

这句话的字面意思是“我又不是昨天才出生的”，可引申为“自己不需要对方叮嘱也懂”

情景：

Salesgirl: You can take this car into consideration. It works well and its price is reasonable.

Todd:I was not born yesterday.
托德：我又不是小孩，别骗我了。