Feeling like you're living two lives: one inside your story and one in the world. (Bonus problem: the fictional story feels more real.)
Getting waaaaay too excited about my characters and having to remind myself that they are not real.
My first National Novel Writing Month and I'm almost to the 8,000 word mark! So far I've only faced mild writer's block, major inkstains, and a few hand cramps, but I supposed I can consider those occupational hazards. 🙂