Moodiness and irritability are quite common and the way a woman responds is very individualized. Sleep deprivation or interrupted sleep can often lower our boiling point so, if you can, concentrate of sleep and naps which means modifying your normal routine and letting some of your responsibilities go unattended. Calming therapies such as chamomile tea, meditation, etc may be helpful. While some calming herbs work well, their use in pregnancy is usually not advised due to lack of information about those herbs in pregnancy. It's difficult to evaluate herbs and drugs in pregnancy and most information is from animal studies. Adequate rest is still the best especially as the baby grows and causes more discomfort.