How do you come up with something "original"?

[billy]

leanne in the forum
limericks abound
haiku hides in fear

The short answer is:  you don't.  Sorry.  There's nothing new under the sun, as some dead bloke once said.

What you can come up with is a new way to say something old, because although you're not especially unique either (bad luck, emos, people actually do understand you... although I'm not guaranteeing they care), you do have a set of experiences and abilities that is at least a little bit different to the next person's.  

Someone once told me (or I might have been talking to myself, I forget) that poets create windows where others see only walls.  Someone else once told me (again, can't guarantee it wasn't an internal voice) that poets twist the world sideways and use words to show others that view.  

And if all else fails, write rude limericks, because there just aren't enough of those in the world.  Too many bloody haiku.