You can use your monthly hormone cycle to plan your schedule and make the most of your relationships, says Gabrielle Lichterman, author of the new book 28 Days: What Your Cycle Reveals About Your Love Life, Moods, and Potential. Here’s a day-by-day map for managing — and enjoying — your friendships. Day 1 is the first day of your period. Count forward from there.

Days 1-3:

As your cycle begins, low estrogen has you feeling introspective and quiet. You prefer to stick close to home, and you may not feel like ­chatting with friends as much as usual.

Days 4-10:

Rising estrogen and testosterone are pumping up your energy. You want to be social and are making plans with friends and coworkers accordingly. You’re feeling happy and close to your loved ones.

Days 11-13:

Peaking estrogen and testosterone have you at your boldest and most daring, so you may be ready to try things you were too shy to try even just a few days ago. You’re at your most talkative, too, so friends and family should be prepared with open ears.

Days 14-17:

Your estrogen and testosterone take a dip in these pre-PMS days, when many women are ovulating. As a result, you may be finding fault with your friends, mate or children. You also may feel slightly blue or irritated. Rising progesterone makes you more sedate, so keep activities mellow.

Days 18-22:

Estrogen and testosterone rise, putting an end to pre-PMS irritability (for now). Progesterone continues to rise, too, which turns down the volume on excited emotions. So if you can’t muster a cheer when your friend tells you she won a free cruise, she shouldn’t take it personally.

Day 23 - Cycle’s end:

PMS hits on these days as estrogen, progesterone and testosterone levels all descend. As you know, these are the days you are most likely to feel moody or short-tempered. Because you might not be feeling very social, you may want to stay home with a good friend, a pizza and some chocolate to feed your PMS cravings