Even though the person they love isn't there when they think about them it makes them happy.
When the sun comes out it makes you feel happy and it's the same as if you were to reunite with your love it's like they are your sunshine and your happiness.
When there is a storm they think of the person they love and it seems as if the sun had come out.
The person said nothing could come between the but when they left and returned the person had left for someone else.
It broke the persons heart.
While they are away and dream about their loved one and than they wake up it breaks their heart to be away from the person that makes the gray skies go away.
YOU ARE MY SUNSHINE, MY ONLY SUNSHINE YOU MAKE ME HAPPY WHEN SKIES ARE GREY YOU NEVER KNOW, DEAR, HOW MUCH I LOVE YOU PLEASE DON'T TAKE MY SUNSHINE AWAY THE OTHER NIGHT, DEAR, AS I LAY SLEEPING I DREAMT I HELD YOU IN MY ARMS WHEN I AWOKE, DEAR, I WAS MISTAKEN SO I HUNG MY HEAD, AND I CRIED YOU ARE MY SUNSHINE, MY ONLY SUNSHINE YOU MAKE ME HAPPY WHEN SKIES ARE GREY YOU NEVER KNOW,
DEAR, HOW MUCH I LOVE YOU PLEASE DON'T TAKE MY SUNSHINE AWAY I'LL ALWAYS LOVE YOU AND MAKE YOU HAPPY IF YOU WILL ONLY SAY THE SAME BUT IF YOU LEAVE ME TO LOVE ANOTHER, YOU'LL REGRET IT ALL ONE DAY YOU ARE MY SUNSHINE, MY ONLY SUNSHINE YOU MAKE ME HAPPY WHEN SKIES ARE GREY YOU NEVER KNOW, DEAR, HOW MUCH I LOVE YOU PEASE DON'T TAKE MY SUNSHINE AWAY PLEASE DON'T TAKE MY SUNSHINE AWAY.