It's basically telling you what happens when you party too much and get really drunk. Partying all night and day having fun, enjoying the moment and living life. And then there is the part where she says "you wake up in the morning... " yes, it's the after-effects of partying. The headache, the weird dreams. That could be reality. Waking up in a strange place and all that other weird stuff. Great song. I hope it never dies.