“Never esteem anything as of advantage to you that will make you break your word or lose your self-respect.”

All of posted quotes are good, but this is a more important one. "This thou must always bear in mind, what is the nature of the whole, and what is my nature, and how this is related to that, and what kind of a part it is of what kind of a whole; and that there is no one who hinders thee from always doing and saying the things which are according to the nature of which thou art a part." -- Marcus Arelius Meditation, Book II.

We hold this truth to be self evident !

When my children were growing up, I would remind them that they are only as good as their word, and if their word means nothing, then they have nothing.  Don't become good at lying, otherwise that will become what you are most skilled at doing.  Self-respect is paramount — retain your honor, no matter the cost.