Riddle?

Guess the word or phrase I've been wanting to tell you.


Youth vanishes when I always come
Over me is the brightest light
Under me are lovers looking at me

At morning, I can't live
Rest is my duty on morning
Every night I come to work

To be more than a billion years old
Rough work it should be
In times, I get tired but still rocking
Covering darkness to light
Keep on working to give you path
End is impossible for me
Darkness never prevail.