Happy Birthday !!
One overindulgent meal or less than perfect day of eating WILL NOT make or break your healthy lifestyle. There are going to be days you eat more than others. It happens. As long as it doesn't happen every single day, you'll be fine. Try to eat moderately, but if you do overindulge, don't beat yourself up. For the rest of the week, you do your best to eat more mindfully. no guilt necessary.
Remember, you don't have to be perfect to be healthy. A slice or two of cake, some wine, French fries, etc. CAN all be a part of a healthy lifestyle as long as you are mindful of the portion.
Have fun, but not too much fun. ;)