such sweet sorrow

 

Clicking around a bit, I see that tons of people don't get Juliet's joke when she says "parting is such sweet sorrow that I shall say goodnight till it be morrow."

Romeo & Juliet can't stand to leave each other, even though it's getting later and later. 

They say "goodnight," but keep embracing; ... "goodnight," but still embrace; ... then, "parting is such sweet sorrow that I shall say goodnight till it be morrow."

That is, if they keep going at this rate they're going to be saying goodnight when it's no longer night.