The 2nd principle is what I use for my fitness/nutrition, and what I suggest to my clients. Ok, so you really want that donut, thats fine. Absolutely have it tomorrow. Just do 6 more meals of clean eating, and then tomorrow if you want that donut, have it. But usually, you get through a whole day of eating well and you feel good and now you have a streak of X meals that you’re hesitant to break. Usually, the donut doesn’t meet mouth until cheat day.