When life sends misery your way, spit in life's face and make your own happiness. I'd refuse the offer and make the best of my circumstances: just because someone tells me I'm going to be miserable when someone else is happy, just because they're happy, doesn't mean I'm going to just lie down and accept it.
I think in some way in real life an individual's happiness is tied to other people's anyway: people always want what they can't have, or feel pride and satisfaction when they have what other people don't. You have two choices, the way I see it: you can accept it and suffer, or you can reject it and focus on your happiness, and not on someone else's; you can live your life, independent, and make of it what you want to make of it.. If someone offered me that deal, I'd turn it down and be laughing at the misery life tried to throw at me as I carried on with my life in the knowledge that things would get even better for me after I'd died...or that, at least, they wouldn't get any worse, because I hadn't accepted the offer.