Always, take care that your mouth protector must fit you snuggly against your upper teeth, without needing to bite or clench your jaw. If you have to clench your jaw or bite to keep your mouthguard in place, then your mouth protector certainly does not fit you right. Again, your mouth protector must stay securely and tightly on your upper teeth. By the way, see if it is protecting your roots, and does not hinder your speech, to ensure you have the right fit.