She Quotes (page 41)
She was filled with a strange, wild, unfamiliar happiness, and knew that this was love. Twice in her life she had mistaken something else for it; it was like seeing somebody in the street who you think is a friend, you whistle and wave and run after him, but it is not only not the friend, but not even very like him. A few minutes later the real friend appears in view, and then you can’t imagine how you ever mistook that other person for him.
Nancy Mitford