First of all, track your menstrual cycle and the different symptoms you experience through each one. This can be physical or emotional. It impacts everything. The whole body gears towards whatever its reproductive goal is, so nothing is exactly left untouched. The "period" is only the end of the sentence so to say. Take note of any irregular patterns, like having too frequent or infrequent periods, notice if certain events or habits trigger a late period or other phase. No phase is a compartmentalized thing.
Anyway, I have always had a long menstrual cycle (around 45 days rather than about a month) with a shorter period (3-4 days) and recently the last two years developed ovarian cysts (PCOS is just a cluster of symptoms related to a hormonal imbalance likely related to adrenal fatigue, chronic inflammation, and or thyroid issues).
Through the luteal phase, specifically into the PMS week I find myself hopelessly insecure, more prone to depression/irritability/confusion, wanting reassurance and safety, feeling more reserved, trouble with concentration, less pleasure in daily activites like eating and other "fun stuff", trouble concentrating, feeling more victimized and sensitive. It cycles between jittery anxiety/panicky, being socially off/irritable, and being really down/depressed, until it all slows down and the tears wash it all away and the period comes. My woo woo way of looking at it is with my history of trauma and stress, plus current stressors, my feminine cycles are there to identify, digest, and purge all of that pain in the week or so leading up to the shedding of the old.
I've learned to write down specific triggers and signs of these experiences so I can better point to them the next time and remind myself that feelings are felt, not necessarily real. More sitting and just having a steady breath. Calming herbal teas. More solo outings to familiar calm places. Watching funny things and letting myself vent in a journal. Letting myself scream and cry and hit the pillow. I don't just say these feelings are stupid or pathological nor do I let them dictate my life/relationships. I keep to myself and let out the worst of it away from people with my own internal validation/reminders there to guide me. I remind myself of my accomplishments and good qualities even if they are small.