The Encheiridion, or Manual (36-38)

As the proposition it is either day or it is night is of great importance for the disjunctive argument, but for the conjunctive is of no value,[*] so in a symposium (entertainment) to select the larger share is of great value for the body, but for the maintenance of the social feeling is worth nothing. When then you are eating with another, remember to look not only to the value for the body of the things set before you, but also to the value of the behaviour towards the host which ought to be observed.[*]

If you have assumed a character above your strength, you have both acted in this matter in an unbecoming way, and you have neglected that which you might have fulfilled.

In walking about as you take care not to step on a nail or to sprain your foot, so take care not to damage your own ruling faculty: and if we observe this rule in every act, we shall undertake the act with more security.