Maybe you have never thought about it, but the nervousness and fatigue before menstruation can be caused simply by lack of sleep. Researchers say that, because of TV, computer or commitments that keep us up late, every day we get at least an hour less sleep than our ancestors. Yet sleep is a very precious and fragile gift, which must be treated carefully. The risk could even be a lowering of immune defences. Make sure you get enough sleep and, in the evening, slow down the pace before going to bed: this helps you to wind down and put the body in sleep mode.