The rule of friendship means there should be mutual sympathy between them, each supplying what the other lacks and trying to benefit the other, always using friendly and sincere words.
All I can do is to urge on you to regard friendship as the greatest thing in the world; for there is nothing which so fits in with our nature, or is so exactly what we want in prosperity or adversity.
Civilized people are taught by logic, barbarians, by necessity, communities by tradition; and the lesson inculcated even in wild beasts by nature itself. They learn that they have to defend their own bodies and persons lives from violence of any and every kind by all means within their power.
In fact the whole passion ordinarily termed love (and heaven help me if I can think of any other term to apply to it) is of such exceeding triviality that I see nothing that I think comparable with it.
To give and receive advice - the former with freedom, and yet without bitterness, the latter with patience and without irritation - is peculiarly appropriate to geniune friendship.