Since we're currently working on the hypothesis that we are cycle-syncing over the Internet, illustrator I Heart Guts' menstrual flow-chart is both handy and topical. Legends like "Day 13: HORMONE PARTY!" and "LUTEAL LUNACY!" make bleeding seem...fun.
In the first 1-2 days of your period, your estrogen is low, which leads to fatigue. Also, most women know the hellish cramps these two days bring. This is a good time to exercise a bit. It may ease the cramping!