On my world there were several songs that I kept singing, depending on my mood and weather conditions....
"Both sides now" by Joni Mitchell (happy times or sad!)
"Comfortably Numb" by Pink Floyd (when doing a lonely, foggy mountain climb)
"Sad Lisa" by Cat Stevens (when I am really grinding up a hill)
"Land of Make Believe" by the Moody Blues.
there are others, but these were the big four on my world tour.
roughstuff