Who said this old saying, Never let them see you break a sweat.?

Question

and also please please try to tell me more like that thanks

Answer 1

"Never let them see you sweat!" was coined by a "Dry Idea" deodorant commercial...

The phrase "no sweat" was popularized by the Korean War in the early 1950s, and the phrase "Don't sweat the small stuff" appeared soon thereafter.

A similar quote I can think of is 'Illegitimi non carborundum' - 'Don't let the b******s grind you down.'