One day things changed. One day she woke up different. She realized that because someone didn't know how to handle her heart, wasn't a fault of hers, but his.
She began to pick up each piece and put it back together one at a time. She has now put a guard around it to protect it. She protects it because she has made the effort to mend her own heart and will no longer give the key to just anyone.
Pick those pieces up and press on.