“At least I thought it was a wall. It sure felt like one. It was hard. It was flat. It stretched out on either side of me. You know… wall.”

Part I, Ch. VI : The Cross and the Contrast
The Pilgrim's Progress (1678), Part I
Context: Now I saw in my dream, that the highway, up which Christian was to go, was fenced on either side with a wall, and that wall was called salvation. Up this way, therefore, did burdened Christian run, but not without great difficulty, because of the load on his back. He ran thus till he came at a place somewhat ascending; and upon that place stood a cross, and a little below, in the bottom, a sepulchre. So I saw in my dream, that just as Christian came up with the cross, his burden loosed from off his shoulders, and fell from off his back, and began to tumble, and so continued to do till it came to the mouth of the sepulchre, where it fell in, and I saw it no more.

Jerusalem Prize acceptance speech, (2009)
Context: If there is a hard, high wall and an egg that breaks against it, no matter how right the wall or how wrong the egg, I will stand on the side of the egg. Why? Because each of us is an egg, a unique soul enclosed in a fragile egg. Each of us is confronting a high wall. The high wall is the system which forces us to do the things we would not ordinarily see fit to do as individuals... We are all human beings, individuals, fragile eggs. We have no hope against the wall: it's too high, too dark, too cold. To fight the wall, we must join our souls together for warmth, strength. We must not let the system control us -- create who we are. It is we who created the system.

Gwenhwyfar
The Mists of Avalon (1983)

It's just flat."
Comedy Central Presents, S01E06: Mitch Hedberg https://www.youtube.com/watch?v=iAHiHJ2AhYE&feature=youtu.be (5 January 1999)

Source: Lord of Misrule

Jace and Clary, pg. 244
Source: The Mortal Instruments, City of Ashes (2008)
Context: "I wish I could hate you. I want to hate you. I try to hate you. It would be so much easier if I did hate you. Sometimes I think I do hate you and then I see you and I-"
"And you what?"
"What do you think? Why should I tell you everything about how I feel when you never tell me anything. It's like banging my head on a wall, except at least if I were banging my head on a wall, I'd be able to make myself stop."

Animal Dreams.
Animal Dreams (1990)
Variant: The very least you can do in your life is to figure out what you hope for. And the most you can do is live inside that hope. Not admire it from a distance but live right in it, under its roof.
Source: The Bean Trees

Heimsljós (World Light) (1940), Book Three: The House of the Poet