This is weird but I can always tell how bad AF is going to be based on my symptoms. If I don't get many symptoms and proceed on an even keel, AF is just the worst. Like, get out the heating pad and cancel my plans, it's time to lay on the couch and moan with pain for two days and then be grumpy and uncomfortable for three or four more days. On the other hand, if I get terribly moody beforehand, get headaches, and have a massive sweet tooth, it's always a light and easy three or four days. I hate sweets, they always make me sick, but last week I was at the grocery store and suddenly decided that I had to have ice cream, and then I tore the house apart looking for the oatmeal cream pies DH always has stashed somewhere. Sure enough, AF just ended after three-ish light, non-crampy days.