Can someone tell me what exactly this means and how to respond, if I reply at all?
Most Helpful Guy
"You don't know what you have until you lose it"
This is common after breakup. I would be cautious because if he has you again he will soon forget and leave you again.
Most Helpful Girl
He knows he made a mistake and will probably ask for you back, DONT go back. He'll do it again, unless he works incredibly hard to get you back, then you know he cares