Mark Twain, A Connecticut Yankee in King Arthur's Court

"You can't depend on your eyes when your imagination is out of focus."

"But it is a blessed provision of nature that at times like these, as soon as a man's mercury has got down to a certain point there comes a revulsion, and he rallies. Hope springs up, and cheerfulness along with it, and then he is in good shape to do something for himself, if anything can be done."