Friendship - False friendship - what makes a true friendship?

Jesus speaks how a true friend can express what he feels. According to Jesus, one way someone can express his friendship is through his willingness to give up something valuable to him for the one he regards as a true friend. However, it is also so important for us to understand that it is possible that a friend can put us in danger. Some may see this as a contradiction. But it is not. Why? Apostle Paul tells us in his letter to the Corinthians: “In my many travels I have been in danger from floods and from robbers, in danger from fellow Jews and from Gentiles; there have been dangers in the cities, dangers in the wilds, dangers on the high seas, and dangers from false friends” (II Cor. 11:26, Today’s English Version).