When Andrew learns that Mary Hatcher is already engaged, he feels relief. At least there won’t be another flirt in his library. This relief is short-lived, though; unknowingly, Mary begins to win him over.
Sooner or later, we all learn what true love is like. The journey isn't easy, though. You make mistakes and later reflect on how silly you were--chasing an infatuation, thinking it would be your happily ever after!