Someone once asked me if when a person who walked out of your life could ever return? I said, "there's once where I lost a button, and when I've got the same button back I've decided to wear another shirt." Such is fashion of human relationships: there's no "coming" or "going", only whether if you cherished the times you shared together - and it goes the same for both friendship and romantic relationships. In a person's lifetime if there's someone who ever truly loved you, even if he/she has left your life - that is true happiness - doesn't matter if they're just memories.