"To live in the hearts we leave behind, is not to die."
"we leave behind"and ",is not to die."
What do that mean?

Question

Answer

The hearts we leave behind are the family/friends/people who knew us before we died.

Is not to die means that if we are remembered by people we have not died and been forgotten.

Answer

Actually it's incorrect. It should read:
To live in the hearts we leave behind, is to not die.

Answer

Hi,

to fail or forget to bring someone or something along. - John was sick, so we had to leave him behind. Oh, I left my money behind.

I'm not so clever. I got the answer here for you: http://idioms.thefreedictionary.com/leave+behind