One day of overeating does NOT offset all of your progress.
Let’s walk through this example so you can see exactly what I mean.
For these purposes, let’s assume you find out that your maintenance calories are 2200. In other words, if you eat that amount every day, your weight won’t change. You decide you want to lose weight, so you aim to eat 1800 calories every day (a deficit of 400 calories every day)
Everything is going great, but Saturday is a holiday. By the end of the day, after all of the drinks, snacks, and dessert, you end up eating 3200 calories, which is well over your target.
It’s easy to feel like you messed up and that you offset your progress. But look at the week as a whole. Even though you overate on this one day, you are still in an overall deficit for the week.
Is the deficit as large as you planned? No. In fact, it’s half of what it would have been if you hadn’t overate on Saturday. But you did, and that is TOTALLY FINE.
A deficit is still a deficit. Progress is still progress. One day doesn’t make you a failure. In fact, if you look at the big picture of the whole week, it was actually a success, since you are still in a deficit overall.
Whether you overeat (or under eat) by 200 calories or 2000 calories, it’s only one day. You can remain perfectly on track. Small progress is still progress.