Man is so built that he cannot imagine his own death. This leads to endless invention of religions. (from Stranger in a Strange Land by Robert A. Heinlein)
Nothing contributes so much to tranquillize the mind as a steady purpose,—a point on which the soul may fix its intellectual eye. (from Frankenstein by Mary Shelley)
Being in the company of a fool can be like looking in the mirror. You may not like what you see but you need it to remind you who you don't want to be.