Start by wearing your heart on your sleeve. You don't know any better yet, up to this point the world has been good to you. When your heart starts catching on door knobs and being battered against the black top, you carefully tuck the gently scratched ***** in your pocket.
In your pocket, out of sight it's a little harder for the bruises to land. Over time the blood stain of time spent hidden seeps through. When the first blow lands it knocks the wind from you. You still don't lock your heart up. You just move it back into your chest.
You don't sew yourself shut, cracked ribs spread wide, a tourniquet wrapped around one chamber, the abused ***** still trying to beat it's an erratic rhythm, but it's a pulse. It's not even shocking, when daggers come from the front or behind and twist into the gnarled flesh.
Arterial spray, broken pieces you've given away, cover the walls. Bones curl around to try to protect you, but you've never been able to close yourself off completely. The worst part is, you sort of enjoy the pain. For a moment, the heart remembers before the first bruises marred the skin, before you built a cage to exist within.