Mirrors

I used to hate mirrors. But then I figured out that what a person sees in a mirror is only a perception of a reflection, not the reflection itself. In a mirror, we see ourselves physically. But we actually only see what we allow ourselves to see. Imagine having to see yourself as the rest of the world sees you. Seeing yourself through someone else's eyes. It's a cruel thing. Perhaps that is because there is a certain amount of comfort in the illusions we paint for ourselves. Illusions that would be crushed were we ever forced to know how everybody else sees us.
A friend is that way. A true friend. A best friend, perhaps. They show you who you are. The darker, nastier side of you which, when looking into a mirror, you can choose not to acknowledge. A best friend hands this to you with no qualms about it, and is still willing to be your friend anyways.
But for some people, I would imagine this can be quite frightening. I would imagine that when a friend knows you that well, they know you too well. And then, you're in dire straights to "un-know" them and distance yourself from them as much as posible. But by that time, it's too late. A friend, moreover and especially a best friend, will always show you who you are without fear. Because a best friend is honor-bound by some unspoken code of best-friend-ness to do so. Best friends work for the betterment of each other. And in doing so, they show each other themselves, and the part they would each rather not see.