Varies for me,some times cool as a cucumber on nice bucks,other times pretty jacked up on a doe.If I feel liked I am pinned on a deer the excitement heightens.If I am cold and have adrenaline going at the same time I am more jittery.I actually purposely over dress in some instances so I can not have my body be tense from the cold.
A couple of mantra's for me are reminding myself to keep the tension out of my body especially my hands and legs.Secondly to focus of the execution of an excellent shot.