That's ok. Get your food optimising book, check out the low syn options in the back.
Fill up with something before you go out, if you're hungry, you're more likely to think "blow it",
Look at what's on the menu, and plan ahead so you know what you're having. Have a side salad as well.
Save your syns for the evening, so you can keep within the 15. Factor in any alcohol, and alternate with a diet coke or diet soft drink, or water.
I always think to myself
"what do I want more? A blow out, or a good weight loss?"
The weight loss usually wins, and that helps me stay in control.
If the blow out wins, I know what to expect. But I try and get straight back on plan for the rest of the week, and I'd be happy with a small loss!
hope that helps! xx