To thine own self be true, and it must follow, as the night the day, thou canst not then...

Polonius, Lord Chamberlain: There, my blessing with thee. And these few precepts in thy memory look thou character. Give thy thoughts no tongue nor any unproportioned thought his act. Be thou familiar, but by no means vulgar. Those friends thou hast, and their adoption tried, grapple them to thy soul with hoops of steel, but do not dull thy palm with entertainment of each new-hatched, unfledged comrade. Beware an entrance to a quarrel, but being in, bear that the opposed may beware of thee. Give every man thine ear, but few thy voice. Costly thy habit as thy purse can buy, but not expressed in fancy. Rich, not gaudy, for the apparel oft proclaims the man. Neither a borrower nor a lender be, for loan oft loses both itself and friend and borrowing dulls the edge of husbandry. This, above all: to thine own self be true, and it must follow, as the night the day, thou canst not then be false to any man.