When my 8 year old wants an extra dessert or something else not on the board, I typically say no. I say it with a smile. She doesn't need another fudgesicle and she isn't going to get one and my telling her so only hurts for a minute. She's fine.
I get the best results when I Mommy myself. When I simply say, No, you don't need that-- to another bite of chocolate, or the diet soda I want to quit, or a few of those Tostito chips that are, after all, whole grain, right? (Wrong. At least in the ways that count.)
Saying no when you're undernourished or starving is not really an option, unless you have some powerful agenda at stake. But I'm not undernourished or starving. I work plenty of treats into my life, food and otherwise. I'm far from deprived. So when I say no, I'm giving myself the same thoughtful treatment I take so seriously with my kids.
It only hurts for a minute. I'm just fine.