I thought I'd post what I found out in a blog too.  Another member was cranky on day 6 and I remember that's about the time that I too felt that grouchy, PMS, down right mean feeling.  I'm on day 11 and it's gone now.  I did a little checking on a few websites to find out more information about it.

Well, since carbs boost serotonin, it's the sudden decrease in carbs that's doing it. 

I just did a Google search and found this:  "Deprived of its usual foods, levels of serotonin and beta-endorphin (chemicals in the brain that regulate feelings of happiness and well-being) quickly begin to drop. The result: fatigue, depression and crankiness."  from this site:  http://tinyurl.com/46dendn

And here's another one:  http://www.cbsnews.com/stories/2009/11/10/earlyshow/health/main5602883.shtml

We can't have a baked potato, until cycle two.  So, in the mean time try to get both your fruit servings in before 2pm.  I seem to always go past 2pm and miss my second fruit serving.  Oh, and don't forget exercise and your 64 oz of water.

I hope that helps.