What is a "cheat" day?

I have heard that some people who are living a healthy lifestyle or dieting temporarily (not smart) give themselves a "cheat" day during which they are allowed to eat more than usual, or eat less clean foods. It can range from eating whatever you want, all day, to eating about 500 calories more than you usually do, to eating the same amount of calories but allowing yourself to have ice cream or something. Some say it's good to shock your body by eating more than you usually do once in a while to keep your metabolism up. However, I find that hard to believe. Eating a lot, especially of junk or processed foods, tends to spike the blood sugar and thus insulin, which leads to our bodies storing more fat even when we switch to clean foods. I think that having the same diet all the time is actually ideal, because we teach our bodies to be fat burners by giving them a dependable schedule of calorie and nutrient intake. When we let our blood sugar get down too low by not eating, we train our bodies to hang onto every calorie they get and store them as fat instead of burning them. Rather, I think it's healthy to allow ourselves little "cheat" moments in which we give into strong cravings for food, or when we really want a bite of something delicious from a friend's plate at a restaurant, and loosen our restriction rules to live realistically. In the end, I would rather take actions that will contribute to my ability to eat healthy for life than actions that will help me lose an extra pound, which I will eventually gain back, this week.

Thus, I have to come to the conclusion that I don't approve of my Thursday night actions of eating cookies and drinking vodka. Of course drinking made me really tired, so I also didn't do my Insanity workout. Today I had to do double Insanity again. It's really a bad habit for me to skip because I don't think doing two workouts in a day is as beneficial as doing the intended workout every day, and I feel that it's a slippery slope.