TNCOM, #10

He established that, while it might be rare for a man to be driven insane, little was required to tip the balance. All that was needed was a slight shift, and nothing would be as it formerly was. In these deliberations, Casanova likened a lucid mind to a glass, which does not break of its own accord. Yet how easily it is shattered. One wrong move is all that it takes. —W.G. Sebald, "All'estero," in Vertigo