Eat correctly.  

Changes in hormones cause a drop in blood sugar which can cause us to feel AWFUL.  I used to get intense nausea, feel light headed and the panic attacks would start.  So I learnt to eat every 3 hours; DAY AND NIGHT no missing!  A high carbohydrate diet - lots of sandwiches, cakes, bananas, dried fruit and nuts.  If the blood sugar drops it can take 10 days to even out again.  And it is most likely to drop in the 10-14 days prior to the period beginning.  You don't eat more, you just spread out a good variety of foods throughout the 24 hours.

It takes 3-4 months to be aware of a difference.  If you forget then the body has to 'make up' the sugar levels during the next month.

If I felt well I forgot to eat.  I would suffer soon after.  So would hubby!  :;): but he learnt to remind me to carry snacks at all times.  Where ever I was.  I used to take my own food with me when we visited anyone because they eat at different times and I *had* to stick to every 3 hours.

Progesterone supplements helped too.  But I still keep to my 3-4 hours especially if I am in a particularly anxious situation.

Have a look at the UK NAPS site - National Association for Pre-menstrual Syndrome - for up-do-date information.