First step to preventing hair breakage is conditioning. When you condition your hair, try and find a strengthening shampoo and conditioner set, which many different brands offer. With long hairstyles you have to leave your conditioner on for at least 60 seconds, this way the conditioner really gets to the roots and scalp keeping your hair soft and healthy.
It is also important, especially with long hair since most people with long hairstyles become so tempted to throw their hair up with a ponytail holder, that you only use holders with no metal. You can find these in the hair care section at most any store, even the dollar store! Just make sure to never use the ponytail holders with the little metal part on them; it can rip your hair out causing more unsightly breakage.
Another important part of preventing breakage is combing your hair from the bottom up. After showering especially it is really helpful to comb your hair using a wide toothed comb rather than a bristle brush and start at the ends working your way to the roots. This will prevent the breakage involved in ripping through your hair from top to bottom with a brush. Although with long hair style especially, this method can be time consuming, it really is worth it and you will see a big difference.