Tracy, ONE day, such as a family birthday will not affect your ultimate success as long as you don't let that one day turn into a "birthday week" as we all know these things can do. So, if there was one day with Chinese food and pizza, so be it. But, get back on track immediately!
This happens in my family during February. We have my birthday and my son's two days apart from each other. There is usually a special dinner out for my birthday and my son's separate of each other, then we each get our own cake. Yikes! This year, I chose not to have a cake of my own and had a leftover slice of his cake. We combined dinners out for us both. For Valentines Day (14th, his b-day is the 16th and mine is the 18th) I requested absolutely no candy whatsoever. It was a more successful week than usual.
I have a problem with Christmas, for example, as it becomes "the holiday season" and all the special foods that we get one time during the year are so hard to resist.
I should try to make a few of those "special" foods at other times during the year so that I can recognize that they are not just holiday foods and I could have them at other times. This way the binging won't occur? Just an interesting thought. Wonder what my family would think to come home to me making candy cane cookies during July?

I tend to gorge myself on a few items that are just so well loved that I cannot resist them. I use the thinking, "but I can only have them once a year" and blow it.
At any rate, Tracy, do watch Chinese food. I reserve that for the most absolute special occasions due to the high sodium content. Every time I eat it, I have a gain that week. If my family goes to the Chinese Super Buffet near our house, I have found out that they have a take out menu and I can order the chicken and steamed Chinese vegetables and not do the usual buffet thing with them. It's not as much fun, but I can at least join them.