You could be lovelorn because of unrequited love, loving someone who's unavailable or who simply doesn't feel the same way; or lovelorn from the loss of love. A lovelorn poet might write a melancholy sonnet, and a lovelorn teenager might listen to sad songs and cry in his room. The poet John Milton is often credited with coining lovelorn, a combination of love and lorn, a very old-fashioned way to say "lost" or "ruined."