Why are all the best romances tragic?

Last night I was watching "The English Patient", which is a wonderful movie and I highly recommend it to anyone who hasn't seen it, and it got me thinking, why are all the great love stories tragic? Why do they all end in death and loss? I realize not every love story ends badly, but lets be honest, most of the good ones do.

There's "Atonement." Two lovers separated before they can even have a shot at being together, and then die before they're reunited. Beautiful, but tragic.

There's "Titanic." Pretty similar to "Atonement." Rose and Jack are separated by horrible circumstances out of their control, and Jack dies, leaving Rose to hold onto their love alone. Tragic.

How about "Moulin Rouge?" Amazing, fantastic love story. Satine and Christian overcome the odds to be together, and then she dies and he's left alone. Fucking tragic.

I'm sorry, what's that? Those aren't classic love stories you say?

Okay fine, how about "Wuthering Heights?" That's a classic and a tragedy. Katherine and Heathcliff can't fight their feelings for each other but are too stubborn to admit it, and then she dies and they lose the chance. So sad.

I've got another one. "Gone With the Wind," freaking sad. Scarlet spends the majority of the story pining after Ashley, completely blind to her true match in Rhett. By the time she figures it out, Rhett's had enough and he leaves her. Tragic.

And I mean, what about the ultimate tragic love story, "Romeo and Juliet?" Say what you will about it, but these two died for their love. What's more tragic then that?

And of course, the movie that started this random train of thought, "The English Patient." Laszlo and Katherine loved each other so much, and lost each other because of war and hate. So fucking tragic.

Why is it that love and sorrow go hand in hand? Is it because they are such similar emotions, and you can't love someone without eventually losing them too? Do we believe, as a culture, that a love like the ones in these stories, a love so passionate, so powerful, so agonizingly beautiful, simply cannot last forever? Do we feel the need to kill this love early and fast, while it's at its strongest point, before it slowly dies on its own? Why can't a love like these ones last forever? Who says it can't?

How do we know that Jack and Rose wouldn't have been together forever? That Romeo and Juliet wouldn't have been badass bocce ball players at the old folks home? That Christian and Satine wouldn't have spoiled their grandkids rotten?

I believe love like this does exist, for those of us who have the courage and resolve to wait for it and not let fear and pessimists tell us that its not real. And I believe love like this can last, despite what the cynics say. And no one can convince me differently.