Will I get fat after the party? What do I do to avoid this?

I'm on a diet plus exeraise weight loss plan. And I started it at the end of August and I wanted to congratulate myself on losing 10 pounds so I ate half a cup of vanilla icecream yesterday. BUT! Today it turned out that I had a party! At the party I didn't want to get fat but I did not want to be a party pooper so I ate 2 brownies and a cookie and now I feel like I'm going to get really fat! I also drank juice with it too! What do I do? Will I gain a pound? How do I avoid this? Should I starve myself tomorrow and do intense exercise? I am 14 years old and a freshwoman in highschool.
Will I get fat after the party? What do I do to avoid this?
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