Tough Cookie

자신만만하고 늠름한 사람, 강인한 사람, 만만치 않은 사람

She has become a tough cookie after being harassed by her fellow workers. (그녀는 동료들에게 시달리고 나더니 강해졌어.)

[출처] ● tough cookie (만만치 않은 녀석)-대구토익학원/대구영어회화학원/대구어학원|작성자 엉뚱녀

A: I heard Nancy and James broke up, I wonder how James is doing.
B: Don't worry about James. He is a tough cookie.
    But Nancy is probably broken into pieces. 

< 원문 : http://venticle.blog.me/40132765688>