I, who have never willfully pained another, have no business to pain myself.

You don't have to turn this into something. It doesn't have to upset you. Things can't shape our decisions by themselves.

No longer talk at all about the kind of man that a good man ought to be, but be such

From Apollonius I learned freedom of will and undeviating steadiness of purpose; and to look to nothing else, not even for a moment, except to reason.

Remember that the sole life which a man can lose is that which he is living at the moment.

Don't go on discussing what a good person should be. Just be one.

Always follow these two rules: first, act only on what your reasoning mind proposes for the good of humanity, and second, change your opinion if someone shows you it's wrong. This change of mind must proceed only from the conviction that it's both correct and for the common good, but not because it will give you pleasure and make you popular.