His lover is complaining about him and wanting him to do more. The typical thing a lot of people sometimes think at some point - that their lover isn't doing enough for them. But he's saying that he treats her right and there's no one who'll treat her better than him. He's saying that if she already thinks she's lonely in the relationship, she'll really know the meaning of being lonely when he's gone. The memories of him will haunt her. She'll realize how good he was to her when he's gone.
His lover is complaining about him and wanting him to do more. The typical thing a lot of people sometimes think at some point - that their lover isn't doing enough for them. But he's saying that he treats her right and there's no one who'll treat her better than him. He's saying that if she already thinks she's lonely in the relationship, she'll really know the meaning of being lonely when he's gone. The memories of him will haunt her. She'll realize how good he was to her when he's gone.