You've been in love, of course! If not you've got it to come.
ON BEING IN LOVE. by Jerome K. Jerome - The Literature Page
What does it mean?
'I assume you have already been in love; if not, you will be one day'.
A better title would have been You've been in love, of course!
Extract from the Posting Guidelines:
'Thread titles should include all or part of the word/phrase being discussed.'