When you vomit into a plastic shopping bag with holes in it and it all drips down onto the floor... when you then proceed to clean it up with an old t-shirt that you spontaneously decide you won't need any more, stuff the whole thing into another plastic bag... and wake up next to all that, on the floor, hours later with a pounding headache and yet more vomit in the sink.
When you wake up ON the bed as opposed to IN the bed, with your shoes still on.
When you wake up in the morning and you have no idea how you got home...
When you wake up in the morning when your cellphone rings and when asked where you are you have to admit that you don't know...
When you wake up and it feels like there's a furry animal living in your mouth and a hoard of elephants trampling inside your head, and you say to yourself: "I'll never drink again!"
Crap drug really, when taken in excess, alcohol is.