know thyself

Secondly, thou must keep in view what thou art, striving to know thyself, the most difficult thing to know that the mind can imagine. If thou knowest thyself, it will follow thou wilt not puff thyself up like the frog that strove to make himself as large as the ox; if thou dost, the recollection of having kept pigs in thine own country will serve as the ugly feet for the wheel of thy folly.