This poem says to not give your everything to certain people. Many of them are always changing and once they do, it can hurt you. It tries to explain to not get too comfortable with some people since the ending result can leave you with a painful memory.
"love is different. love is choosing to serve someone in spite of their filthy heart. love is patient and kind, love is deliberate. love is hard. love is pain and sacrifice, it's seeing the darkness in another person and defying the impulse to jump ship.