The propositions which are true and evident must of necessity be employed even by those who contradict them - Epictetus

People find particular things, however, frightening; and it's when someone is able to threaten or entice us with those that the man himself becomes frightening.

Continually remind yourself that you are a mortal being, and someday will die. This will inspire you not to waste precious time in fruitless activities, like stewing over grievances and striving after possessions.

Any person capable of angering you becomes your master; he can anger you only when you permit yourself to be disturbed by him.