What's the meaning behind Cee-Lo's song Forget You?

Here are the lyrics: link

What I'm wondering is: what is the relationship between "you" and the girl he loves?

I understand that "you" is his ex and now he sees his ex with his new love. But then later he says "I still love you" which makes me think that "the girl he loves" is his ex...I don't know

So who are the characters in this story and what are their relationships to each other?
What's the meaning behind Cee-Lo's song Forget You?
Post Opinion