It was Pride that changed angels into devils; it is humility that makes men as angels. - St. Augustine
The Sin of Pride is said by some to the the foremost of the Seven Deadly Sins. Hubris is the gateway through all other sin enters the mortal soul.
What it is
Pride is excessive belief in one's own abilities, that interferes with the individual's recognition of the grace of God. It has been called the sin from which all others arise. Pride is also known as Vanity.
Why you do it
Well-meaning elementary school teachers told you to "believe in yourself."
Your punishment in Hell will be
You'll be broken on the wheel.
Associated symbols & suchlike
Pride is linked with the horse and the color violet.
Medieval theologian Thomas Aquinas said of Pride "inordinate self-love is the cause of every sin (1,77) ... the root of pride is found to consist in man not being, in some way, subject to God and His rule."
The Travelers' Guide to Hell says that
Pride is ruled by the celestial sign of the Sun. It is "the mother of all sins... the thin line between righteousness and self-righteousness." Incidentally, this book actually mentions the Seven Deadly Sins Home page. Right there on page 6!
Of the seven deadly sins, pride is the only one with a virtuous side. It is certainly a good thing to have pride in one's country, in one's community, in oneself. But when taken too far, as Michael Eric Dyson shows in Pride, these virtues become deadly sins.