A similie

Writing is like puking (also called vomiting/ throwing up/ barfing/ being sick/ chucking/ regurgitating/ expectorating/ honking <this one is my favorite>/ heaving/ spewing).

• It happens when you've had too much of a good thing or any quantity of a bad thing.
• If you have to do it, you just HAVE TO do it, and if you don't get to an appropriate venue fast enough, you'll just do it wherever you are.
• It is often brought on by getting drunk/high.
• If you analyze your puke/writing after you're done, you can see samples of all you've ingested/experienced in the past few hours, like a lot of watermelon seeds or an underlying strain of melancholy. (I think these two are sort of similar, because I'm pretty sure that the seeds feel melancholic without the loving embrace of the juicy watermelon they had been born into.)
• Even if the end results (i.e. the puke/writing) are not that good, you feel immensely relieved once it's all out. (If you're thinking that puke can't ever be good, I urge you to stare at it for 10 minutes straight the next time you do it. The beautiful patterns that emerge from slimy food that has been digested and expelled from the wrong orifice are stunning.)

If this were a maths theorem, I would end this with "Hence, proved", but since it isn't, I won't.