Sorry you didn't feel good yesterday.
I do agree with katie though, if you can think positive then you feel better.
Also, every time I think about food and think I'd like to eat that, instead of feeling sad because I can't, I remind myself that I am making the choice to be thin. I could eat whatever I want but I've been doing that for years and it doesn't make me thin. Doing this diet makes me thinner and I want that more than the food.
I did find as well that once I was past the second week, it got a lot easier - you get into the swing of things more and start forgetting the cravings.