Help! I wanna be the best cross country runner at my school?

It sounds like you have the physical exercise in the bag but have you considered just what foods are needed for endurance? A lion can only pul a plow 20 or 30 feet before it must stop to rest but a horse or mule can plow all day long. - The key is natural carbohydrates that are still attached to fiber. They release sugar slowly into the blood stream and give you endurance while simple sugars from processed foods are absorbed rapidly and then you have a lot of blood sugar for a short time followed by low blood sugar. So eat whole wheat bread, cooked oatmeal and rid yourself of the power drinks and soft drinks and sugary foods. Your stamina will increase and you will feel better all day long. God bless you.