If the heart is a house, relationship would be the door.
An open hearty house is one which the person gladly welcomes the people in, having a merry time. But then, with this naive and innocent outlook, one tends to get hurt. Sometimes, the door of relationship is scarred, or maybe even carved on, causing one to slightly pull the door closer and not so open.
But still, there's a chance to prove the host's point of view wrong. But the person is probably already more narrow-minded, so be careful with what you say or you'll leave another scar for the host to remember. And one more scar could mean a lot worse.
When one is traumatized with an event that happened with a previous person, the host could do something out of emotional hurt. The host might close the door of relationship tightly shut, lock the door and throw away the key into the darkest depths of the sea. And even if you try to break the barrier down, sometimes, you've just have to realize you've lost them. Leaving you, as a friend or a family member, unable to connect and communicate with them.
However, locking the door could have benefits. Maybe if you have found the happiness and the love of your life, you could live a content, blissful and secure life. No one could break down the door, and you are happy with what you have in the house. You need not to ever leave your comfort zone, for you could have all you ever wanted.
Well, that's just how I see it. Which side of the door are you on people's hearts today?