Beginning at puberty, a woman's ovaries start releasing estrogen in coordination with each monthly menstrual cycle. At mid-cycle, levels suddenly spike, triggering the release of an egg (ovulation). They then fall just as quickly. During the rest of the month, estrogen levels climb and fall gradually.
Normal estrogen levels vary widely. Large differences are typical in a woman on different days, or between two women on the same day of their cycles. The actual measured level of estrogen doesn't predict emotional disturbances.