1.Don't be tricked twice by the same person.
吃一堑长一智。
2.Try as you may, it is impossible to deny your nature.
你尽管尝试，但否认你的天性是不可能的。
3.Better the evil you know than the one you don't know.
明枪易躲暗箭难防。
4.It's better to teach than simply to tell.
身教比仅仅言传更好。
5.Necessity is the mother of invention.
需求是发明之源。