In many ways, your monthly hormone cycle can be seen as a yin-yang, with two distinct halves that are the mirror opposites.
For instance, in the first half (Week 1 and Week 2), rising estrogen is pushing you out in the world, making you curious, confident and urging you to connect with others.
During the second half of your cycle (Week 3 and Week 4), a double-dipping of this hormone combined with progesterone pushes you to do just the opposite—stay close to home, stick to things you know and explore your inner world.
In some cases, women may have extreme versions of these two parts of their cycle. (In fact, researchers out of the London and PMS Menopause Centre have cautioned doctors who diagnose some women with bipolar disorder to explore whether severe premenstrual syndrome is the true diagnosis.) Other women may find the difference is subtle.
You can find out a little more about how the two halves of your cycle affect you by reading the overview of your monthly cycle here.