If you're putting too much pressure on yourself (as far as diet and exersize go) that can make you crabby too! I know when I was super strict about what and how much of everything I ate, id get frustrated that I was missing out on food I loved. Then I would take it out on anyone that was a little annoying. It was not a happy time. I gave up trying to lose weight and gained back everything I had lost. This time I'm losing weight at about the same rate, but I'm eating what I want. I'm happier and I think (hope) this time it sticks with me.
"If you have it (love), you don't need to have anything else, and if you don't have it, it doesn't matter much what else you have." - J.M. Barrie