It's Sad the Lover's Validity of Stay Together when Expires?

On the beach
They walk hand in hand
When Sun goes down
They were separated!
She left for North
And he went to South.
The following day
Sun rises in the East
And I am sure sets in the West.
Another couple on the beach
And where do they go
Secretly I watch?

(Amy Winehouse: July 23: Found dead in London at the age 27.)