Why do lovers break each others hearts?

Baby do you know what you did today? Baby do you know what you took away? You took the blue out of the sky My whole life changed when you said goodbye And I keep cryin', cryin' Oh baby, oh baby I wish I never saw the sunshine I wish I never saw the sunshine Cause if I never saw the sunshine baby Then maybe I wouldn't mind the rain Every day is just like the day before All alone, a hundred miles from shore All of my dreams, I dream with you Now they will die and never come true And so I'm cryin', cryin' Oh baby, oh baby I wish I never saw the sunshine I wish I never saw the sunshine Cause if I never saw the sunshine baby Then maybe I wouldn't mind the rain There wouldn't be this pain And I know there wouldn't be Cloud that's over me everywhere I go Oh baby, oh baby I wish I never saw the sunshine I wish I never saw the sunshine But if I never saw the sunshine baby Then maybe I wouldn't mind the rain I wouldn't mind the rain Oh, that pain Oh, that rain That sunshine