To the person who is my friend, I would say they love me not only when they praise me but when they reproach me as well, when they criticize me and when they correct my mistakes.  It is not the actions of a friend to praise your wrongdoings as well as your good actions, but rather that of a deceiver and a sarcast.  

However, to praise when needed, and to criticize when something is done wrong, this is the mark of a friend an guardian... the enemy therefore I do not accept, not even when he praises.. The friend however I accept even when he criticizes me. The enemy is disgusting even when he manifests love towards me, the friend on the other hand even when he delivers  wounds to me is desirable. 

The kiss of an enemy is full of suspicion, where as the wounds committed by a friend are a result of guardianship. That is why it is said that, "I place greater trust in the wounds that are caused by a friend, then the kiss of an enemy."

Source: Taken from Saint John Chrisostomos' letters to the Ephesians.