Yeah, it is a bit unnerving. I remember question 76 coming up, and feeling like I was going to throw up in my mouth - I could feel myself start to panic a bit. Took a few deep breaths, kept going. When the 2-hour "do you want to take a break" screen came up, I kept going. When the blue screen popped up after question 120, I nearly cried - I was mentally exhausted.
You know how they take a picture of you before you go in? There should be one taken AFTER you're finished - the "Before/After" pics would be priceless.
I went home, cried since I figured I'd failed, then I went to a yarn shop and bought some tasty expensive yarn and chilled out!