It's one of the seven deadly sins, and theologians consider it the deadliest, as most sins flow from injured pride, frequently called crimes of passion.
An extreme love of self diminishes our love for others. Diminishing other people can make them appear as less than human, diminishing our compassion for them.
When we look in a mirror is what we see real?
In a way, the image looking back is reversed. Notice when you try to do something like brush your hair, its easier to feel what you're doing rather than use the reflected image as a guide. The concept of an alternate, or distorted reality has intrigued imaginations for centuries.
In literature the mirror is a symbol of an alternate world where reality is distorted or worse, the truth is revealed. Examples are "Alice in Wonderland: Through the Looking Glass" and The Grimm Brothers "Snow White."
When the wicked queen chanted : "Mirror, mirror on the wall," the mirror reflected her image, but when the answer wasn't what she wanted to hear she became enraged and planned Snow White's demise. Was the mirror image a distorted image?
The queen was beautiful, but her vanity made her ugly. It took the form of the witch and the witch was her true self.
Snow White never looks in anything reflective. She is buried in a glass coffin so the prince could see within the outer shell to the real person within the shell. Snow White's beauty isn't reflective, its real. She washed the dwarves dishes and cleaned the house (we will ignore the minor trespassing issue.)
The opposite of pride, Snow White was selfless. She served without being asked. In this story beauty and ugliness are reflected in deeds and appearances are decieving.
The idea of the magic mirror may have been inspired by the real life Countess Bathory. She was hailed as one of the most beautiful women in Eurpoe. Her vanity became an obsession and her cruelty was reknowned. It was her belief bathing in virgin blood would keep her young and beautiful. At least 80 (some say up to 600) women suffered for her distorted reality.
Dream interpreters will tell you when you dream of looking in a mirror you are in a stage of growth and self discovery. If your eyes are closed in the dream, you may not accept who you are. If you see another person's face or an animal instead of yourself, it means you worry you don't know yourself.
You may want to change yourself in some way to be sure the reflection is a real reflection of you.