Hormonal shifts can make some women lose sleep, which in turn may make them irritable. It is generally important to get enough sleep to level out moods. Premenstrually, sleep becomes crucial. Try your best to get seven to nine solid hours of Z's per night. Many women even feel the need to nap during the premenstrual week — if you can manage a quick few minutes of sleep in the middle of the day, indulge. It may make the difference between a good day, and a day of snapping and tears.