Obviously, if you're on a pill that has a row of inactive pills during the week that you get your period, nothing is going to happen if you forget to take one of them, according to the Mayo Clinic. Those pills are often called "sugar pills" or "placebo pills," because they don't contain any hormones or active ingredients , according to the American Congress of Obstetrics and Gynecology. You just have to make sure you know which day to start your next new pack of pills, but otherwise, you can skip them. If you're on a progesterone-only pill, though, then you won't have a week of inactive pills, so it's crucial to take each pill every single day, for your whole cycle.