Treatises on Friendship and Old Age. Marcus Cicero

if they did manage to keep them up to adolescence, they were sometimes broken by a rivalry in courtship, or for some other advantage to which their mutual claims were not compatible. Even if the friendship was prolonged beyond that time, yet it frequently received a rude shock should the two happen to be competitors for office. For while the most fatal blow to friendship in the majority of cases was the lust of gold, in the case of the best men it was a rivalry for office and reputation, by which it had often happened that the most violent enmity had arisen between the closest friends.

      Again, wide breaches and, for the most part, justifiable ones were caused by an immoral request being made of friends, to pander to a man's unholy desires or to assist him in inflicting a wrong. A refusal, though perfectly right, is attacked by those to whom they refuse compliance as a violation of the laws of friendship. Now the people who have no scruples as to the requests they make to their friends, thereby allow that they are ready to have no scruples as to what they will do for their friends; and it is the recriminations of such people which commonly not only quench friendships, but give rise to lasting enmities. "In fact," he used to say, "these fatalities overhang friendship in such numbers that it requires not only wisdom but good luck also to escape them all."