HOW COULD THIS BE TRUE

HOW IS IT THAT MY HEART IS FILLED WITH HAPPINESS
YET MY HEART IS ALSO BLUE
HOW IS THAT WHEN YOU ARE WITH ME
MY HEART TELLS ME WHAT TO DO
HOW IS IT THAT WHEN YOU ARE AWAY
I FEEL SO ALL ALONE
YET I HAVE YOU WHEN I NEED YOU
ON THE OTHER END OF A PHONE