Having your first period does not only mean that you are going to bleed once a month, it means that your body is now following a calendar all its own, and that calendar is shaped like a circle. It is like the changing of the moon, the tides and the seasons.
Your body changes in subtle ways throughout the cycle, and the more you pay attention, the more you will notice them. On the opposite side of the circle from menstruation is ovulation. Your body temperature changes when you ovulate. Around that time you smell better and see better. Your vagina might give off slick clear or white discharge, the white mate to the red of your period.
If you pay attention you might notice there are patterns to when you are neat and when you are sloppy; when you are clumsy and when you are sentimental; when you feel sharp and organized and when you feel imaginative and inventive; when you feel run down and when you feel like you could run for miles.
Every day is not the same. You are not like a robot which never changes. In fact, you change constantly, and this is a good thing. Learn your unique patterns and follow their lead as you plan your time. If you understand your menstrual cycle, you know yourself that much better. The best way to do this is to keep some sort of menstrual record. This can be anything from marks on a calandar to notes in your diary, or you can keep a special chart just for your cycle, which makes it easy to compare month by month.