Ive just started the diet, after beginning on a raw food diet last year and failing.  Recently I went on vacation in Toronto and Montreal, and the breads and beers there are amazing!  So when i came back, I researched the paleo diet, and quit all the neolithic foods cold turkey.  I also amped up my excercise by walking 4 extra miles a day(to work) on top of walking all day at work(waitress in a bar-hence the love of fine beers and breads )
I had an amazing amount of energy for the first 5 days, and never felt the debilitating hunger pains between meals(its difficult to eat during working hours).
As of now, I am exausted.  Last night and today, all I have wanted to do when 7o clock rolled around was crawl into my bed and fall asleep!  Maybe its the World Cup , but this seems very sudden.  Is there a drop of energy I should have expected?  Maybe lack of grain based carbs? 
Please help!  Im too young to be this tired so early!!!