The 20% is NOT for indulging cravings like this. It's for having corn on the cob (or potato salad or pie or beer or all of the above) this Wednesday.
I suggest you go for a walk. Tell yourself you can have a donut later. As you pass the donut shop, tell yourself you'll stop on the way back. When you pass it again, tell yourself you'll have a donut on your walk tomorrow. I swear this works for me really well.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Highest squat: 167.5 x 2. Current Deadlift: 190 x 3