"Sad love. The concept is seemingly as ineffable as love itself, although most people understand exactly how sad love feels. Separately, sadness is felt as a heavy emptiness that may be coupled with a yearning to have what is unattainable or to bring back what was lost. Love adds intensity and complexity to sadness: the desire, passion, or craving experienced with love become flavored by the anguish, dejection, and helplessness felt with sadness.....
As a psychotherapist, people often describe to me their sadness as a result of love--often as the ghost that remains of the good things about a relationship that has ended or is about to end. The beautiful memories, not the ugly ones, are those that trigger what I would now describe as sad love. And sad love evokes further reminders of what once was, in stark contrast to the actuality of the present. In vivid emotional memory, sad love holds on tight to what has been lost or to what is fading away....
Researchers who studied the concept of love among people in the United States, Italy, and China found that it has both similar and different meanings cross culturally, including the presence of love-related concepts among Chinese people, such as "sad love," "sorrow-love," and "tenderness-pity" (Rothbaum & Tsang, 2004). In reading that study of emotions I came across the notion of sad love which, in all my years of practice, I unfortunately had not encountered. Finding a way to articulate the experience of sadness can provide relief to those who cannot find words for what they feel. In this vein, Shakespeare wrote in his play, MacBeth, "Give sorrow words. The grief that does not speak whispers the o'er-fraught heart, and bids it break." Similarly, the concept of sad love struck me as a descriptor that profoundly and succinctly captures the emotional impact of love that has gone sadly."
See the entire article about the emotion described as "sad love" @ Psychology Today