Happy Birthday!
That said, I think what you mean is that you can come up with justification to overeat just about every time you're in a restaurant. Is that correct? If so, then this really is a mental habit that you'd do well to break.
Your body doesn't care whether it's your birthday, Christmas, the 4th of July, your great-nephew's graduation from daycare, or whatever--if you consistently overeat, you'll consistenly gain weight.
Make a deal with yourself. Plan ahead. Decide ahead of time as much as possible exactly what you're going to have when you go out, and then stick with your choice. It's not the last meal on earth, and you'll have other opportunities to choose any old food you like. But for right now, since you want to lose weight, stay with your plan.
The other thing to watch out for is alcohol. For some people, all it takes is half a drink, and suddenly the deep fried cheese appetizer seems like a good idea. So then, not only are there the empty alcohol calories, but the fat and carb calories as well.
Hang in there! One birthday doesn't "ruin" anything!
Jay