Nothing's impossible. You say it's impossible to be with her, but that's just not true. Just have faith and believe in yourself and with enough time and effort, you'll discover that love can concur all!
Just kidding, you're fucked! Sucks to be you!
HA! Ok, seriously.... I know how you feel. Hell, I think everybody's been through this one at some point in their lives. Being in love with someone who can't or won't love you back is fuckin' rough. It's even rougher if you think you might have a chance (and I get the impression that you think you MIGHT have a chance) if not for outside forces. Social divisions like class, race, age, wealth, and even gender (if you're in love with someone of the same gender and they're not homosexual) can vastly over-complicate matters that SHOULD be simple. In an ideal world, being in love should be enough for two people to be together, but as I'm constantly reminding people, the world we live in is FAAAAR from ideal!
You say it's "impossible" and I can only take your word for that since you didn't give details. If it's really impossible, then no advice I can give will help this situation to hurt any less and there's certainly nothing I can do to make it possible. You wanted a sympathetic ear, so okay. You got one. Hell, you got more than one. Of all the people who'll read this, I'd guarantee that 90% of them have been where you are now (myself included). You'll learn to deal with it over time and with experience.
Oh yes, you'll have more experience with this! You think this is the last time you'll fall in love with somebody you can't have? Pssh! Puh-lease! It's gonna happen again, right up until you find "the one" and get married and then you'll spend the rest of your life with that special someone. But guess what? It'll happen after that too! That's a little bit of real-life "happily ever after" shit that nobody ever warns newlyweds about. You WILL fall in love again with someone else even AFTER you're married!
And you'll handle it the same way you're forced to handle it right now. The difference between a mature responsible individual and a douchebag, is that the douchebag will "follow his heart" (and his dick) to wherever it leads. An intelligent thinking person knows when he can't (or shouldn't) go chasing after bullshit. Thankfully though, by the time you're married, you SHOULD be responsible enough and have enough experience with unrequited love that you'll be able to handle it far more easily than you can now.
Don't get me wrong, though. Though it'll get easier, it'll never really be easy. This is just part of the human condition and you'll be fine. Just don't do anything stupid and, for fuck's sake, don't follow your fucking heart! That's retarded.
But, then again, what do I know? You gave me shit for details, so maybe it's not "impossible" and maybe you'll find a way. If you can find a way that doesn't fuck over everybody involved, good for you. If not, don't be a drama llama. Suck it up and accept reality.
Happy Fucking New Year,