If people would have an unbreakable heart, life wouldn't beas hard. Our heart causes us pain. If we love someone and they pass away, what happens? Our hearts stop beating for a little bit. When our love relationships go down hill, or end, what happens? Our heart is broken. When you have a secret and you tell it to your best friend, and tell them not to tell anyone, what if they tell the whole school, or work place? You get heart broken, and mabey even embarrased. When you get caught staring at your crush, what happens? He notices and might tell you to leave them alone, or say something about you, so you get your heart broke.
There are an infinity amount of things that can break your heart. Think about it, wouldn't life be easier if our hearts were unbreakable. But it wouldn't be life if we didn't get hurt once in a while.