updated by @windwolf: 01/15/17 03:17:22PM
I feel that when this happens, it's triggered by a self preservation mechanism. Nature is at work, trying to protect you from over exerting yourself emotionally when it might completely drain you.
When I touch the energy around the events you are describing, where you felt you empath skills fading, I feel it was just to protect your heart, pulling away from too much exposure to difficult emotions.
I don't feel this is a reason for concern. When your heart is strong, this will all come back