When Anaxagoras was told of the death of his son, he only said, "I knew he was mortal." So we in all casualties of life should say "I knew my riches were uncertain, that my friend was but a man." Such considerations would soon pacify us, because all our troubles proceed from their being unexpected.
PlutarchSo also it is good not always to make a friend of the person who is expert in twining himself around us; but, after testing them, to attach ourselves to those who are worthy of our affection and likely to be serviceable to us.
Plutarch