the world > action or operation > failure or lack of success > fail or be unsuccessful [verb (intransitive)] > fail to maintain a level of achievement (2)
figurative. Intellectual or mental hold; power to apprehend or master a subject. to lose one's grip (cf. lose, v.1 3d).
Of a person: to fall away from a standard (in behaviour or achievement); to deteriorate; to lose one's command of things. Chiefly as present parti…