Friendship, then, like the other natural loves, is unable to save itself. In reality, because it is spiritual and therefore faces a subtler enemy, it must, even more wholeheartedly than they, invoke the divine protection if it hopes to remain sweet. For consider how narrow its true path is. Is must not become what the people call a "mutual admiration society"; yet if it is not full of mutual admiration, of Appreciative love, it is not Friendship at all.
C.S. Lewis, The Four Loves
friendship, love