My horse won't calm down! Helppp?

Don't worry! She is probably just bored! you can go to any horse tack shop and pick up some lick-it thing, or anything she can nibble on. Put some hay in the corner of her stall, and if she eats it too fast, put it in a hay bale carrier with a small hole to make it harder to get it out and cause her to be less antsy. Whenever you are out in the barn, walk her around a bit, even if you aren't riding. Good luck with your mare, Happy Trails!