Thanks to Eric for letting me know about this interesting study done a few years ago on rejection. According to this study, the pain we feel after being rejected, by a love, friend or through shunning (like the jw's do), is processed in the same part of the brain as physical pain. So a "broken heart" indeed feels like it's actually physically broken.
I find this interesting because it's been proposed that Fibromyalgia, a neuromuscular condition I was diagnosed with at age 17, may be caused in part by a sensitivity in the brain area that detects and regulates our response to physical pain. I know I've always been acutely aware of my own and other's pain, both emotional and physical. I've been known to "vibe" the pain off others and spend hours in agony after being with someone who is experiencing physical or emotional distress. It affords me deeper experiences of love and empathy but rejection hurts like hell. I feel some days like carving out my heart, just to make it stop aching. Sigh.