If you allow yourself to eat whatever you want for 2 meals out of every 21, you won't inflict enough damage to subvert your weight loss. And you'll feel less deprived.
A fat lady stands in a bus. A young handsome man crashes into her unwillingly and sais: - I´m sorry I haven´t seen you... And the lady sais: - Oh you flatterer...
Another good joke:
"When I am frustrated I eat chocolate. But then I cannot slim down and I am so frustrated of it that I eat chocolate again..."