If God made man to take a broken heart and become weak, it had to be for a good reason. After all, man was created to be the strong one. I don't think anyone can honestly say why hearts get broken and what if any is a way to prevent it from happening. People say that "Men" were created to become the leader and main supplier of all that was needed in life. What if all that was needed in life was to care and show affection and no one knew that the man had no way to provide without the one thing he needed most of all, a woman. No person has the ability to show love unless there is someone to accept it. It goes back to the saying, "If a tree falls in the middle of a forest and no one is around, does it make a sound?"
Sometimes when a guy is feeling weak from being pushed over the edge, the result can cause him to resort to his primal instinct of cornering himself off from any and all threats that he feels may harm him. If this is true then why open yourself up to the possibility of being hurt in the first place? Maybe for the slightest glimmer of hope? Perhaps, or maybe its just that he never truely understands what it is in life that he needs to shield himself from to prevent further heartache.
