From my research and experience, a closed heart is not something we choose, it is something that happens. Oftentimes after a profound betrayal of trust, a mechanism inside of us is tripped causing us to believe the reason we were betrayed, hurt or abandoned is because we dared to love.
We blame our broken heart on our open heart and vow to never let another person hurt us again. We wall up and close down.
We continually attempt relationships from behind a barricade (closed heart) only peeking out occasionally to see if the coast is clear. We form the mindset: When I know for sure I am accepted then I will open up. Thus we withhold the secret ingredient needed for deep connection – an open heart/vulnerability.