My HormonologyHeather, a Hormonology newsletter subscriber, asks: “Which part of your cycle is the best for running errands? I certainly learned the hard way this week never to do it during Week 4, I wanted to strangle everyone I came into contact with.”

My answer: As you discovered, your premenstrual Week 4 isn’t one of the best times of your cycle to run errands. People are waaayyy more annoying during this week. That’s due to plunging estrogen, which is bringing down mood-stabilizing serotonin, making you less patient with other folks’ annoying behavior. You’re also more sensitive to noise, light, smells and a jostley, elbowed crowd of fellow errand-runners, which can sour your mood. What’s more, you’re low on mental and physical energy, so having to make choices, split-second decisions and (my least favorite) do college-level math in your head to figure out if something is expensive or a steal using a store’s purposely misleading and confusing unit, sale and price tag numbers, is draining. So, the whole experience is less than ideal.

When you can, I advise doing the bulk of your monthly errands from the second half of your Week 1 through the end of your Week 2 (4 to 14 days after the onset of your period). The rising estrogen during this phase is boosting mood-stabilizing serotonin, which makes it easier to put up with other folks’ shenanigans. In fact, you’re actually happy to mix and mingle with other errand-runners and salespeople despite their shortcomings! That’s because your hormones are pushing you to get out into the world and socialize–even if it means while simply picking up groceries or getting your suit back from the dry cleaner. Even better, this hormonal duo is boosting your mental and physical energy, making all the running around, decision-making and advanced calculus required to do your errands far easier.