I have to disguise them every time I teach my secondary students and not show them that I am angry about their rude behaviour in class.

For what? What could i get with it? I'm what i'm and i feel what i feel, and i don't care what nobody think.

to some extent, yes. but I always show my true feelings. I don't want to suffer heart failure or heart attack!... hehehe... do you believe that not showing your true feelings / emotions will make you look older? express your feelings freely! :)

In a few circonstances you have to... It is a question of politeness right ?

No,I can not. You can know my feeling from my facial expression.