"I'm mad" means you're mad at something I've done. An action. I can fix that! I can apologize, do it differently and move on.
"I'm disappointed" means I am fundamentally wrong. Whatever the action was that made you mad I can't fix because it came from a place of me being broken deep down, somewhere unfixable.
Disappointed to me feels doomed, heavy and terrible.
To me the exact opposite of disappointment is pride.
I feel proud of myself when I make choices that I know are better for me. When I make the choice to do something that will result in a good outcome I feel good! Sometimes there is a delayed gratification on the scale and that sucks! But, the feeling of pride I get when I do something that makes me feel good is instant gratification and it reminds me I'm worth it and it pushes me to keep going.
Feeling proud is like a drug without all the side effects. Feeling proud is a reminder that I am good! I am deserving. I am not broken. I do matter.
Weight Watchers helps me feel proud by putting the power in my hands. I can make any choice I want to make and when I make the choice that makes me feel good, I feel proud. I don't do it because I have to, I do it because I want to and that feels good!