If you don't know what writing is, you may think it is not especially difficult...

“If you don't know what writing is, you may think it is not especially difficult.... Let me tell you that it is an arduous task: it destroys your eyesight, bends your spine, squeezes your stomach and your sides, pinches your lower back and makes your whole body ache.... Like the sailor arriving at the port, so the writer rejoices on arriving at the last line. De gratias semper”

Colophon of a 12th-century Beatus manuscript from Silos

Anyone in the middle of writing a book will strongly agree with the sentiments of this quote!