I usually just give myself a few extra calories on the days when my cravings are really bad and try not to think about it. If I really want that Reese's peanut butter cup I just have it so I can stop craving it and work it into my weekly calories.
I always make sure to get in all my regular workouts though...that's one thing that's non-negotiable, (especially because I often REALLY need that chocolate or whatever). I don't feel so bad if I still managed to do all my workouts. The cramps I get are horrendous to the point where I'm doubled over in pain every night, can't sleep and come home from class in agony everyday and sit in bed with my heating pad... That being said, I load up on midol, drink lots of water and just get through my hour/hour and a half in the gym so I can feel better the rest of the day. I've also found that since I've increased the intensity of my workouts my cramps have been significantly better (I never believed the whole "exercise makes cramps go away" thing until now). It's not just during when I workout either, it's all the time which is fantastic. If that's what working out like crazy gets me...all I can say is thank GODDDDDDD!