the utmost degree of difficulty of a skill which a person can manage, that can be obtained solely in the most reinforcing surroundings. It has been recommended that whenever learning a skill a person moves from the optimal level, where the skill can be performed with help from other people, to the operational level, where a skill can be performed separately but potentially at a lesser than optimal level.

OPTIMAL LEVEL: "The optimal level of achievement is already lower than what you've been scoring on average all year."