dear John letter

[Nefertiti]

Hi there.

" That my love for you has died away like grass upon the lawn"

What does the quote mean? Is it a common usage?

Thanks in advance.

________
The Song BOBBY BARE - DEAR JOHN LETTER LYRICS

[Tdol]

It's not a complete sentence, but means that the person no longer loves the other.

[Nefertiti]

Hi, Tdol.

"My love for you has died away like grass upon the lawn"
Is this a common usage to describe a person no longer loves the other?
It seems grass is always upon the lawn. So what's the significance of it? What's the difference between grass and lawn?

Thanks for your replies.